The Marine Malacofauna of Skokholm Lsland

F.J.A.Slieker, A.F. de H.L.Strack & E.J.O.Kompanjel ' Jongr, Natuurmuseum Rotterdam

The marine malacofaunaof Skokholm lsland

Slieker, F.J.A., de Jong, A.F., Strack, H.L., & Kompanje, E.J.O., 1994 - The marine malacofaunaof SkokhohnIsland - DEINSEA l, 57 - 75 ISSN 0923-9308].Published 15 April 1994.

With the aim of sludying the local malacofauna,the authorsvisited Skokholm_Island(Pembrokeshire, Wales, UK) in 1990 and 1991. hr this paper, known data are supplementedby the results of the authon'fieldrvork. Atotal of l14 specieswere recorded;49 are new records for Skokholm Island, ofwhich four are also new for the Bristol Channelregion. On the basis ofthe current results a marine reservestalus for Skokholm is reconrmended.

De mariene nnlacofauna van Skokhohtreiland - De auteurs bezoclrtenin 1990 en l99l Skokholm Island (Pernbrokeshire,Wales, UK) teneinde een beeld te krijgen van de locale malacofauna" Be- staande gegevens werden aangevuld met veldwaarnerningenvan de auteurs. In totaal werden l14 soorlen geregistreerd,waarvan 49 nieuw voor het eiland, vier hiervan bleken tevens nieuw voor de Bristol Chamel regio te zijn. De auteursconcluderen op basis van de resultatenvan het onderzoek, 'marien dat Skokholm voor de status reservaat' in aanmerkine dient te komen.

Correspondence: c/o Natuunnuseurtr Rotterdarn, P.O.Box 23452, NL-3001 KL Rotterdam, the Netherlands

Keyrvords: malacology, tnariue fauna, Polyplacophora, Gastropoda,Bivalvia, Cephalopoda, Skok- holm lsland,Great Britain

INTRODUCTIONAND METHODS In I 987E. J.O.Kompanje conducted biornetrical Apartfrom the five localitiesshrdied, the follo- studieson seabirdpopulations on SkokholmIs- wing siteswere occasionallymentioned in the land.On his recommendationthe authors visited cardfile system:Tlre Stack,Little Bay, Head theisland between 16th and 23rd June 1990 and Bay, Wild GooseBay, Dumbell Bay, Ravens 10thand lTth August1991 to studythe malaco- Gully, Mad Bay Point, EastBay, Fnnk's Bay fauna. The following localities were investi- andThe Quarry. Most of theselocalities arc very gated:North Haveq PetersBay, SouthHaverl exposed,not easilyaccessible, and according to Hog Bay and CrabBay (Fig. l). An inventory theavailable data, not very interesting;therefore was madeof all availabledata on marinemol- we did not samplethese localities ourselves. luscsin tlre cardfilesystem, stored in theLabor- Collectingwas done by searchingthe solidrock atory of the Bird observatoryon Skokholmls- surfaceand by turningstones embedded in san4 land (seeTable l). Marryof theseearly records or in rockpools.In additionalgae werc collected were previouslypublished by Crothers(1966). and rvashedin freshwater in searchfor living This inventorygave us a goodimpression of the micromolluscs.Collecting methods did not in- collectingsites and ofthe speciesrecorded from clude snorkeling,SCUBA-diving or dredging the islandbefore our survey.All previousrec- thereforethe search-rangewas limited from the ords of marine molluscswere taken behl,een supra-littoralzone down to just beneaththe lo- 1947and 1971 ; no laterrecords could be traced. westlow rvatermark. DEINSEAI, 1994

The resultsof our researchon the different sites Skokholm lies within sea area boundary 21 were influencedby tide level, windforce and di- @ristol Channel)as definedby Seaward(1982, rection. In North Haven and CrabBay shell grit 1990).The islandis 800 m wide with a mzx- was collectedin which many dead micromol- imum lengthof 1.9km andhas about 9.6 km of luscs andjuvenile specimersof larger species ruggedcoastline. Skokholm slopesvery gently werefound. Many of thesespecies occur in the from an altitudeof 50 m at the westemend to 20 shallow subtidalzone. In 1991a low water of mattheclifftops inthe east.Mostofthe circum- spring tides enabledus to extendour search- ferenceis precipitousbut accessto the shoreline rangeby approximately0.65 m comparedto the is possiblein severalplaces and two covespro- previousyear. vide shelteredlandings. Systernaticsand nomenclaturewere used according to Fretter & Graham (1977), Graham (1988),Jones & Baxter(1987), Tebble (19'76) DESCRIPTIONOF LOCALITIES and Thompson (1988). Some material was Nofth Haven (Fig. 2) is one of the two coves preservedfor definiteidentification and is now which provide shelteredlandings and features storedin the NafirurmuseumRotterdam and in the only sandybeach on Skokholm.This beaclu the privatecollections ofthe authors. surroundedby steepcliffs, cornistsof coarse sandand boulders and is only accessibleat low TOPOGRAPHY tide. Skokholm(Fig. 1) is a flat-toppedisland of Old PetersBay (Fig. 3), southof The Neck, is the Red Sandstone,lying 3 kilometers south of leastaccessible locality we havestudied. In the Skomer Island and 3 kilometen west of the littoral mne large boulders dominate. The mainlandcliffs of Marloes in Pembrokeshire, splashzonecontains a relatively large cave Wales,United Kingdom (51'42'N, 05"16'W). (SpiderCave).

Figure I Skokholm lsland;the five investigatedlocalities are indicated by arrows

o loofr Soon! SLIEKERet ol: malacofaunaofSkokholm lsland

(Fig. SouthHaven a) is the othercove that pro- Tabel I Abbreviations of earlier recorders used in the vides shelteredlandings, and is the landing- systematicsurvey, and of tide indications(below) stageforthe serviceboatfromthe mainland. The AD A. Davies(1955) little harbour,with its concretelanding, is sur- BSB B.S.Brookes (1965) roundedby The sheltering cliffs. bottom con- BW B.K.Whitaker (1948-1949) sistsof a reddishlayer of sandstone,derived par- CM C. Metam(1977) ticlesand small stones. CRT C.R.Thorne ( 1956) Hog Bay (Fig. 5) is the smallestof the five lo- HAGS HighArcal Grammar School ( 1966-1969) calitiesstudied. It hasa boulderbeach with few HJM HJ.Moore (1954) smallstones. HJMB HJ.M.Bowen (1948 & 1950) Crab Bay (Fig. 6) is the mostsheltered locality, H]T HJ.Thiel ( lesT) mainly becauseof a group of large rocks (Crab Ju J.Green (1955) Rocks)in front of thebay. Thechannel between JHB J.H.Barret (1948) the islandand CrabRocks is only accessibleat JRP J.R.Povey ( 1965) LWST and scatteredwith many small to me- KST K.S.Thomson( 1955) MEB M.E.Blytheway (1955) dium sized stones,overgrown with Laminaria MJA MJ.Askew (1969 & t972-1973) andSaccorhiza. MPH M.P.Harris (1964) NDP N.D.Purcher (197 l -972) ABBREVIATIONS PDB P.de Brant( | 952) In the systematicsurvey the records may be RBSS R.B.Slone School ( | 963) followedby abbreviations(between brackeG) of UHW U.H.Williams (1950) therecorders who precededus. Their rurmesarc listedin Tabel l. Theyears refer to theperiod(s) LWM Low water mark thepersons and institutions made their observa- LWST Low water of spring tides tions.

Figure 2 Beachat North Haven with large boulders; only accessibleat low tide DEINSEAI, I994

Figure 3 Peters Bay,the least accessiblelocality SLIEKERet ol: malacofaunaof Skokholmlsland I

Figure 5 Hog Bay,the smallest locality studied, at low tide DEINSEAI, I994

SYSTEMATICAL SURVEY OF Acanthochitonacrinita (Perrnrfi. L'7'7'7) RECORDEDSPECIES North Haven, 29.V11.1963,1specimeq South The following classification of abundancy is Haven, 29.VII. 1963, I specimen;South used to indicate the 1990 and 1991 recordings: Haven, 9.VI[.1964, 2 specimers; North Haveq 8.VII.1968, occasional specimens < rare l0 specimens (HAGS);North Haven,10.VII.1969, I spe- scarce l0 - 25 specimens cimen (HAGS). * South Haverq 1990, 5 common 25 - 100sPecimens specimens;North Haveq 1990,I specimen; abundant > 100soeci Crab Bay, 1991, I specimen;Peters BaY, If less than l0 specimenswere recorded,the 1991,I juvenilespecimer exactnumber is givenin mostcases. Habital Intertidal on solid rock, occasionally Habitat notes are only given when live spe- understones. cimenswere observed and are strictly related to conditionson SkokholmIsland. The authors's Acanthochitonafascicularis (Linnaeus, 1767) observationsarel{ceded by an asterisk(*). SoulhHaver! 2.V11.I961,1 specimen (HAGS); NorthHaven" 23.V11.197 l, 3 specimens. Remarks:Most likely these records represenl Class Polyplacophora misidentifiedA. crinita asthey were found on Order Neoloricata overhangingrocks; a habitatprefered by l. Suborder Lepidopleurina crinita but not by.4./ascicalaris. Family Leptochitonidae Genus Le ptochi ton Gr ay, 1847 Class Gastropoda Leptochitonasellus (Gmelin, 179 1) SubclassProsobranchia * No previousrecords from Skokholm. North Order Archaeogastropoda Haven, 1990, I valve in shell-grit; Noth Family Fissurellidae Haven,1991, I valvein shell-grit. GenvsEmarginula Lamarck, 1801

Snborder Ischnochitoniua Emarginulaftssura (Linnaeus,1758) Family Ischnochitonidae No previousrecords from Skokholm.* North Genus Lepidochitona Gtay, l82l Haveq 1990,I specimenin shell-grit;Crab Bay, 1991,4 specimensin shell-grit. Lepidochitona cinerea (Linnaeus, 1767) Hog Bay, 9.VII.1968,1 specimen(HAGS); GensDiodora Gray, 1821 North Haverl 10.VIL 1969, 1 specimen * (HAGS). CrabBay, 1991,I juvenilespeci- Diodoragraeca (Linnaeus, 1758) men;Peters Bay, 1991,3 sPecimers. SouthHaveq3.VIII.1950, I specimenonLami' Habitat:LWM understones embedded in sand. naria-roots(HJMB);Crab Bay, 18.IV.1965,I specimenunder rock at LWST (BSB); Crab Gerus T on i c ella Carpenler, I 873 Bay, 12.MI.1968,I specimenunder stone (HAGS);North Haven, 28.VI[.1969, 1 spe- Tonicellarubra Q,imraeus,1767) cimenat LWST. * North Haven,1990, I spe- * No previousrecords from Skokholm. Peters cimenin shell-grit. Bay, 1991,1 specimen. Habitat:LWM on solid roch shelteredby over- FarnilyAcnraeidae hangingcliffs. GenusA cma e a Eschscholtz, I 833

Suborder Acarrthochitonina Acmaea virgin ea Miiller, 1776) Farnily Acanthochitonidae CrabBay, 2.VIII.l950, 1 deadspecimen SIJMB Genrs Acanthochitona Ctrav. 1821 & UHW); PetersBay, 2.VI[.1950, I dead

E SLIEKERet ol: malacofaunaofSkokholm lsland

sp€cimen(IIJNA & UHW). * North Haverq Haveq SouthHaverl CrabBay, Hog Bay and 1990, I specimenin shell-grit; Crab Bay, PetersBay, 1990-1991,abundant. 1991,I live specimen. Habitat Alwaysat or nearLWM or in pools. Habitat:Underwell embeddedstone atLWST. Remarks:Absent in Head Bay, Frank's Bay, Mad Bay Point and RavensGully according Family Palellidae to observationsfrom 23 to 30.WII.1969. GenusPatella Linnaeus, 1758 Probablythese localities are too exposedfor tlis species. Patellavulgata Linnaeus, 1758 Regularlyrecorded between 1947 and 1973.* Gibbulaumbilicalis (Da Costa 1778) Abundantat all localitiesin 1990and 1991. NorthHaveq SouthHaverq Crab Bay, Hog Bay Habitat:On solid rock andlarge stones in inter- andPeters Bay, 1948-1969,commorl * North tidal zone. Haveq SouthHaven, Crab Bay, Hog Bay and PetersBay, 1990-199l,abundant. Patella depre s s a Penmrg 171 7 Habitat:From mid-tideto low-tidelevelt some- Regularlyrecorde*between 1947 and 1969.* timeshigher in rock pools. Abundantat all localitiesin 1990and 1991. Remarks:Absent in the samelocalities as the Habitat:As P. vulgatabut rarelyabove mid-tide precedingspecies. level. Gibbulatumida (Montagu,1803) Patellaaspera Rdding, 1798 No previousrecords from Skokholm.* North NorthHaven, Peters Bay, SouthHaven and Hog Haver41990, 5 specimensin shell-grit;Crab Buy, 1949-1968, frequent-common;Crab Bay, 1991,2 specimensin shell-grit. Bay, Y .1962,few specimens.* North Haverl PetersBay, SouthHaven and Hog Bay, 1990- Gents Monodonta Lanarck, 1799 1991, abundant;Crab Bay, 1990-1991, scarce. Monodontalineata (Da Costa,1778) Habitat: As P. depressabut in more exposed No(h HaverqSouth Haven, Crab Bay, Hog Bay areasaround low-tide level. and Peten Bay, 1947-1968,scarce; South Haveq 6.VII.1950,n:urow zone of largespe- Genx Helcion Montfort 18 10 cimens in mid-tide region (CM); South Haveq 1959-1962, conrmon (Stanbury, Helcionpellucidunt (Linnaeus, 1758) 19141.* SouthHaverq 1990,scarce; Peters North Haven,SouthHaven, Crab Bay, Hog Bay Bay, 1990,1 specimen;Hog Bay, 1991,2 and Peters Bay, 1947-1969,abundant. * specimens;South Haverl L99I,7 specimens; North Haven, South Haven, Crab Bay and PetersBay, 1991,3 specimens;NorthHaven, Hog Bay, 1990-1991,abundant; Peters Bay, 1991,3specimens. 1990,scarce; Peters Bay, 1991,common. Habitat: Preferssheltered areas around mid-lit- Habitat:Mainly on Laminaria and other large torallevel. brown algae.Often fowrd in Laminaria-hold- Remarks:Absent in the samelocalities as G. fasts (forma laevis).Rarely living understo- cineraria and G. umbilicalis.An extensive nes. studyon a populationof M. lineatain South Haven was conductedbv D.J. Stanburv Family Trochidae (re74). Gems Gibbula Risso, 1826 Genx Calliostoma Swairrson.1840 Gibbulacin eraria (Linnaeus,1758) North Haven,South Haven, Crab Bay, Hog Bay Calliostoma zizyp hin um (Liruraeus,I 758) andPeters Bay,1941-1968, common. * North Hog Bay, Crab Bay, PetersBay, Little Neck Point and The Stack,194'l-1969, only I or 2

d DEINSEAI, I994

specimens.* CrabBay, 1990,I juvenilespe- Lacuna vinda (Montagt 1803) cimen;Cnb Bay, 1991,2 juvenilespecimens; No previous recordsfrom Skokholm. * South SouthHaven,1991, I juvenile specimen. Haveq 1991,common; Peters Bay, 1991, Habitat: Normally, adult specimensoccur in the scarce,Crab Bay andHog Bay, 1991,rare. lowest littoral zone on rocks.The juveniles Habitat: Near LWST, mainly on Gigartina stel- werefound under stones. lata andCeramiumsp.

Family Skeneidae Locunapalhdula @a Costa,11 78) Genus,S/ceneaFleming 1825 CrabBay and PetersBay, 5-12.IV.1948,few specimens(BW); Peten Bay, 1.MII.1950, Skeneaserpuloides (Montagu, 1808) notuncommon (HJMB & UHW). * CrabBay, Plate l, fig. l. 1991, 8 specimens;Hog lay and North No previous records from Skokholm and the Haveq 1991, common; South Haven and Bristol ChannelArea. * NorthHaven,1990, I PetersBay, 1991,abundant. specinrenin shell-grit. Habitat:Near LWST, mainly onGigartina stel- Remarks:The speciesis e4si'foverlookedbe- lata. causeof its small size, or regardedas a ju- venileof anothertrochoid species. Family Littorinidae Gewx Littorina F6russac,1822 Skeneanilens (Phtlipp| 1844) Platel, fig. 2. Littorina liflorea (Linnaeus,1758) No previousrecords from Skokholm.No live Hog Bay andPeters Bay,1941-1969, rare; Crab recordsfrom theBristol ChannelArea. * Crab Bay and North Haverl 1955-1977,scarce; * Bay, 1990,3 live specimens;North Haver; SouthHaveq 1962,abundant. Hog Bay, 1990,I specimenin shell-grit. 1990-1991,scarce; Peters Bay, 1991,scarce; Habitat:Under stones at LWST. SouthHaven, 1990-1991,common; North Remarks:Like the former speciesS. nitens is Haven,1991, common. alsoeasily overlooked. Habitat Mid-littoralon rocksand stones.

Farnily Tricoliidae Littorina neritoides(Linnaeus, 1758) Gens Tricolia Risso, 1826 PetersBay, 11.IX.1949,abundant (GO);Peters Bay, VII.1968,common (HAGS); Hog Bay, Tricoliapullus (Linnaeus,1758) 26.IX.I951, conrmon(CED); North Haven PetersBay, CrabBay and SouthHaverL 1949- and SouthHaveq 1966-1968,frequenttom- 1969, occasional records; North Haven, mon (IIAGS); CrabBay, 1966-1968,abun- * 3l.VII.1950,cornmon on Enteromorphajust dant (HAGS). North Haven,South Have4 below LWST (IIJMB & UHW). * North Crab Bay, PetersBay and Hog Bay, 1990- Haven,South Haven and Crab Bay, 1991, 1991,abundant. abundant;Hog Bay and PetersBay, 1991, Habitat:Upper littoral andsplash zone. scarce. Habitat: Mainly on Gigartina stellata and Ce- Littorinq obtusata(Linnaeus, I 758) ramium sp. near LWST; occasionallyunder North Haveq SouthHaven, Crab Bay, Peters rocks. Bay and Hog Bay, 1950-1973,few specimens.* CrabBay, 1991,scarce; Hog Bay, Order Caenogastropoda 1991,common; South Haverl, 1990, 3 spe- Farnily lacunidae cimens;PetersBay, 1990, 3 specimens;Peters Gents Lacuna Tunton, 1827 Bay, 1991,8 specimens;North Haven, 1990, I specimen;North Haven, 1991, abundant. SLIEKERec ol: malacofaunaof Skokholmlsland

Remarks:Only small specimensof the olive SouthHaven and North Have4 1991,com- greenvariety were found in the littoral zone, mon; PetersBay,1991, abundant. particularlyonFucus. Habitat R. parva as well as the smooth-shelled R.parvaformainterrupta (Adams, 1798) live Liltorina nigrolineataGray, I839 amongred algaein the lower littoral zone. North Haveq VII.|9'77, generallycommon in theP elveti a-zone, especially common :rmong GenusAlvania Nsso. I 826 upper Fucoids(CM). + North Haveq South HaverqCrab Bay, PetersBay and Hog Bay, Alvanio semistrista(Montagu, 1808) 1990-1991.abundant. NorthHaven and Peters Bay, 1-3.MII.1950,not Habitat:On rocksin the high littoral zone. uncornmonbelow LWM ((HJNA & UHW); CrabBay, 2.VI[.1950, 1 specimen(HJMB & Littorinq negledaBearl 1844 UHW). * North HaveiLSouth Haveq Peten North Haven, SouthHaven, Crab Bay, Peten Bay andHog Bay, 1990-1991,rare to scarce; Bay and\OgBay , VIl.l9'77, abundantin the CrabBay, 1990,abundant; Crab Bay, 1991, Balanus-zone,often extendingbeyond the scarce;North Haven,1990-1991, dead spe- Chthamalus-zone(CM). * South Haver; cimerncornmon in shell-grit. 1991,7 specimens;Peters Bay, 1991,com- Habitat:Lower littoral zone,under stones. mon;NorthHaverU 1991, abundant. Habitat:High littoral zone,often in emptybar- Alvaniapundura (Montagu,1803) nacleshells. No previous recordsfrom Skokholm. * North Haveq 1990,9 specimensin shell-grit;Crab Liltorin a sqxatilis (Olivi, 1792) Bay, 1991,18 specimensin shell-grit;North North Haven"South Haven" Peters Bay, Crab Haveq 1991,3 specimensin shell-grit. Bay and Hog Bay, 1950-1973,common to abundant.* This was confirmedby our find- Alvania cancellata(Da Cost4 1778) ingsin 1990and 1991. No previousrecords from Skokholm.* North Habitat:In high littoral zone. Haverl 1990,1 specimenin shell-grit;Crab Bay, 1991,2 specimensin shell-grit. Farnily Hydrobiidae GenusHydrobia Hartmann, 1821 Genx Manzonia Brusirn, 1870

Hydrobiaulvae (Pennant I'777) Munzoniacrassa Kanmacher, 1798) South Haveq l2.VlIJ.1969, 2 specimens No previousrecords from Skokholm.* North (MJA); Hog Bay, 26.VI[.1969,1 specimen Haver; 1990, common in shell-grit; Crab (MJA). Bay, 1991,6 specimensin shell-grit;North Remarks:We did not find it in both 1990and Haverl 1991,6specimens in shell-grit. 1991.As thereis no suitablehabitat for this specieson Skokholm,we believethese two Genu Clngala Fleming, 1828 recordsto be very doubtrul. Cing ula trifasciata(J.Adams, I 800) Family Rissoidae PetenBay, I.VIII. 1950,I live specimen(HJMB Genus Rissoa Desmarest 1814 & UHW); SouthHaverl 3.VIII.I950,I dead specimen (HJMB & [IHW). * Crab Bay, Rissoaparva (Da Cost4 1778) 1990,3 specimens;Crab Bay, 1991,common; North Haven, 3I.VII. 1950, not uncommon Hog Bay, 1990,common; Hog Bay, 1991, (HJMB & UHW); PetersBay, I.VIII.1950, abundan[South Haveq 1990,7 specimens; not uncommonat LWM (HJI\A & UHW). * PetersBay, 1990,4 specimers;North HaverL Crab Bay, 1991,scarce; Hog Bay, 1991,2 1991,I specimen;North Haven, 1990, 2 dead specimens;South Haven, 1990, 2 specimens; specimensin shell-grit. DEINSEAI, I994

specimens.* CrabBay, 1990,I juvenile spe' Lacuna vincta(Moftagu, 1803) I * cimen;Crab Bay, 1991,2 juvenile specimens; No previous recordsfrom Skokholm. South I SouthHaverl1991, I juvenile specimen. Have4 1991,common; Peters BaY, 1991, i Habitat:Normally, adult specimensoccur in the scarce;Cnb Bay andHog Bay, 1991,rare. I lowest littoral zone on rocks.The juveniles Habitat: Near LWST, mainly on Gigartina stel- werefound under stones. lata andCeramium sP. I Family Skeneidae L acuna pallidula (Da Cosa, 117 8) Genus S/ceneaFleming 1825 Crab Bay and PetersBay, 5-12.IV.1948,few specimens(BW); Peten Bay, 1.MII.1950, * Skeneaserpuloides (Montagu, I 808) notuncommon (HJMB & UHW). CrabBay, Platel, fig. l. 1991, 8 specimens;Hog BaY, and North No previous records from Skokholm and the Have& 1991, commoq South Haven and Bristol ChannelArea. * No(hHaven, 1990,1 PetersBay, 1991,abundant. specimenin shell-grit. Habitat NearLWST,mainly onGigartina stel- Remarks:The speciesis easilyoverlooked be- lata. causeof its small size,or regardedas a ju- venileof anothertrochoid species. Family Littorirridae GentssLittorina F6russac, I 822 Skeneanitens (Ptnlippi, 1844) a liltorea (Linnaeus,1758) Platel, fig. 2. Littorin Bay PetersBay,194'1-1969, rare; Crab No previousrecords from Skokholm.No live Hog and Haveq 1955'1977,scarce; recordsfrom theBristol ChamelArea. * Crab Bay and North 1962,abundant. * Hog Bay, Bay, 1990,3 live specimens;North Haven, SouthHaveq scarce;Peters Bay, 1991,scarce; 1990,I specimenin shell-grit. 1990-1991, Haverq 1990-1991,common; North Habitat:Under stones at LWST. South 1991.common. Remarks:Like the former speciesS. nitensis Haven. on rocksand stones. alsoeasily overlooked. Habitat Mid-littoral (Linnaeus, Farnily Tricoliidae Littorina neritoides 1758) (GO);Peters Genus Tricolia Risso, 1826 PetersBay, ll.IX.1949, abundant Bay, VII.1968,common (HAGS); Hog BaY, common (CED); North Haven Tricoliapullus (Linnaeus,1758) 26.IX.1951. Haveq 1966'1968,frequent

Order Caenogastropoda 1991,common; South Haven, 1990, 3 sPe- Family L,acunidae cimens;Peters Bay, 1990,3 specimers;Peters Genrx Lacuna Turton, I 827 Bay, 1991,8 specimens;NorthHaver; 1990, I specimen;NorthHaven, 1991, abundant. SLIEKERec ol: malacofaunaof Skokholmlsland

Habitat:Mid to low littoral zone,under stones. Family Rissoellidae Genus Rlssoella Gny, 1847 Gews Onoba H.& A.Adams. 1852 Rissoellndiaphana (Alder, 1848) Onobesemicostata (Montagu, 1803) Platel, figs.3 & 4 North Haver\ 31.VII.1950,I live specimen No previousrecords from Skokholm.* Crab (HJMB & IJHW); CrabBay, 2$IL 1950,not Bay, Hog Bay, SouthHaven and Peters Bay, uncommon in muddy plEles (HJMB & 1991,abundant; North Haverl 1991,scarce. [IHW). * CrabBay, 1990,Scarce; Cnb Bay Habitat:On redalgae in thelower littoral zone. 1991,common; Hog Bay, 1990,I specimen; HogBay,1991, common; SouthHaveq 1990, Family Ornalogyidae common;North HaverL 1991,8 specimens; Genvs Omalogyro Jefreys, I 860 NorthHaveru 1990, dead specimens common in shell-grit; Crab Bay, 1991, abundantin Omalogtraatomus @hilippi, 1841) shell-grit;North Haven, 1991,16 specimens No previousrecords from Skokholm.* Hog in shell-grit. Bay, 1991,4specimens. Habitat:Under stones,on t€d algaeand some- Habitat:On redalgae in the lower littoral zone. timesin rock pools.Lower littoral zone. Family Skeneopsidae Onobaaculeus (Gould, 1841) Genvs Skeneopsislredale, I9I 5 No previousrecords from Skokholm.* Crab Bay, 1991,2 specimern;Hog Bay, 1990,9 Skeneopsisplanorbis (Fabricius, 1780) specimers;Hog Bay, 1991, 4 specimens; North Haven,2O.VIII.1955, abundant on Coral- SouthHaven, 1991, I specimen;Peters Bay, lina andfrequent but lessabundarx on Lomen- 1991,3 specimens;North Haven, 1990, 2 spe- taria articulata (JG); North Haven" cimensin shell-grit;Crab Bay, 1991,9 spe- 17.V11.1972, I specimen in bamacle(NDP). * cimensin shell-grit. Crab Bay, 1990, 3 specimens;Crab BaY, Habitat:As O. semicostata. 1991,abundan! Hog Bay 1990,5 specimens; Hog Bay, 1991, abundant;South Haver; Family Barleeidae 1990,5specimeq SouthHaveq 1991, l spe- GenusB arleeia W.Clark 1855 cimen;Peters Bay, 1990,'7specimens; Peters Bay, 1991,abundant; North Haven, 1991, Barleeiqunifasciata (Montagu" I 803) abundant. No previousrecords from Skokholm. * Hog Habitat:Mostly on red algaein mid andlow lit- Bay,1990, I specimen;SouthHaven, 1990, I toral zone. specimen;Peters Bay, 1990,8 specimens. Habitat:Living on Ceramiumsp. and otherrcd Family Tornidae algaein the lower littoral zone. Genus Tornrs Turton & Kingston, 1830

Family Cingulopsidae Tornus subcarinatrs(Montagu, 1803) GenssCingulopsis Fretter & Patil, 1958 No previousrecords from Skokholm.* North Haver; 1990,2 specimensin shell-grit;Crab Cingulopsisfulgida (J.Adams,L'7 97) Bay, 1991,I specimenin shell-grit. PetersBay, l7.VIII.l948, rare (JHB); Peters Bay,1.WIL 1950, a smallspecimen (HJMB & Family Caecidae UHW). * PetersBay and Hog Bay, 1991, Genus Caecam Fleming 1813 common;South Haven, 1991, 8 specimens. Habitat:On redalgae in the lower liftoral zone. Ca ecu m glab r um Qvlontaga,I 803) No previous recordsfrom Skokholm. * North Haverq1991,6 specimens in shell-grit. ir SLIEKERet ol: malacofaunaofSkokholm lsland I

Family Cerithiidae Habitat:On rocksin the mid-littonlznne. Gewts B ittium Inach, 1847 Genx Ocenebra Gray, 1847 Bifrium rdiculatum @a Costa,1778) SouthHave4 31.VII.1950,live specimenson Ocenebra erinaceu (Linnaeus, 1758) Halichondria GIJNC & llHW); Crab Bay, Crab Bay, 2.VI[.1950, l juvenile specimen at 18.IV.1965,at LWST (JRP);Peters Bay, LWST(HJMB&rrH!V). 27.Vll.lg7 I, 1 specimen.* CrapBay, 1991,4 specimensin shell-grit. Family Nassariidae Remarks:Previous live recordsprobably referto Geux HiniaLeach, 1852 Cerithiopsistubercularis (Montagu, 1803) as this speciesfeeds on the spongeHalichon- Hinia rdiculala (Linnaeus,1758) dria. SouthHave431.VII.1950, I verywornwashed up specimen(HJNA & UHW). Family Capulidae Genus Capulus Montfo( l8l0 Hinia incrassala(Str

Family Muricidae FarnilyEpitoniidae Genus Nrcella Rdding 1798 GentsEpitonium R6ding 1798

Nucella lapillus (Linnaeus,1758) Epitonium clathratulum (Kanmacher, 1798) Previousas well as prcsentrecords indicate the No previousrecords from Skokholm.* North abundantoccunence ofthis specieson all lo- Haveq 1990,3 specimensin shell-grit;Crab calitiesstudied. DEINSEAI, I994

Bay, 1991,2 specimensin shell-grit;North Subclass Opisthobranchia Haven,1991, I specimenin shell-grit. Order Bullomorpha Family Retusidae Family Janthinidae GenusRelasa Brown, 1887 Gen;s J anthina Plbding, 1798 Rdusa truncatuln@ruguidre, 1792) Janthinajanthina (Limneus,1758) No previous records from Skokholm. * Crab SkokholnL18.VI.1964, I specimenwith dried Bay, 1991,3 specimensin shell-grit. (NPH). up animal in gull-nest ..- Family Rrmcinidae Family Eulimidae GenvsRuncina Forbes & Hanlev. 1853 Genrs Vitreolina Monterosato, 1884 Runcinacoronata (Quatrefages, 1844) Vitreolinaphilippii @ayneval& Ponzi,1854) CrabBay, 22.V1I.1955,1specimen at low tide No previous recordsfrom Skokholm.* Crab (KST);Crab Bay, 27.Y1.1956,1 specimen in Bay, 1991,2 specimensin shell-grit. rock pool (CRT). * Crab Bay, 1990,abundant;Hog Bay, 1990,1 specimen;Crab Bay, Family Pyrarnidellidae 1991,I specimeqHog Bay, 1991,I sPe- Genvs C hry sallida Carparter, 185 7 cimen. Habital Understones in poolsin the lowerlitto- Chrysallidaobtusa @rown, 1827) ral zone. No previous recordsfrom Skokholm.* Crab Bay, 1991,4 specimensin shell-grit;North OrderAplysiomorpha Haverl 1991,3 specimensin shell-grit. FamilyAplysiidae GentsAplysia Linnaeus,1767 Chrysallidaindistinda Montagu, 1808) No previous recordsfrom Skokholm.* Crab Aplysiapundata Cuvier,1803 Bay, 1991,5 specimensin shell-grit. PetersBay, 24.IV.1952,1specimen attached to a rock at low tide level. Genvs Brachystomia Monterosato, 1884 Order Sacoglossa Br achystomia lakisi (Jeffreys, I 858) Farnily Stilligeridae Plate l, figs.5 & 6 Genns Hermaea l,ov64 18,{4 No previous recordsfrom Skokholm.* Crab Bay, 1990,rare; Crab Bay, 1991,rare; Hog Hermaeadendritica (Alder & Hancock,1843) * Bay, 1990,I specimen;Hog Bay, 1991,3 No previousrecords from Skokholm. Crab specimens;North Haverl 1990,3 specimens Bay,1990, 3 specimens. in shell-grit;North HaverqL991,4 specimens Habitat Understones in rock poolsat LWST. in shell-grit;Crab Bay, 1991,8 specimensin shell-grit. Family Limapontiidae Habitat:Under stones at LWST. GenusLimapontia Johnston, 1836

Gel:l.s Odostomla Fleming, l8l3 Limapontia copitata Miiller, 1774) CrabBay, 22.VII.I955,1 specimenat low tide Odostomiaunidentata (Montagu, I 803) (NEB). * Crab Bay, 1990, common;Hog No previous recordsfrom Skokholm. * Peters Bay, 1990,cornmon. Bay, 1991,I specimeqCrab Bay, 1991,8 Habitat:Under stones, often in pools,at low tide specimensin shell-grit. level. Habitat:In Laminaria-holdfastat LWST. SLIEKERet oL:malacofauna ofSkokholm lsland t' Order Nudibranchia beenrecorded. We suspectttnt the singlerec- Family Dotidae ord of Palio nothus (Johnsto41838)was GenusDoto Oken, 1815 misidentifiedard actuallyrefers to the present species. D oto millb oy anu Lemche, I976 No previous records from Skokholm. * Crab PaEonothus (JohnstorL I 838) Bay, 1991,2 specimenson Hydroids. Hog Bay, 6.Vtr.196'7,2specimens under a rock Habitat At low waterlevel under stone. atlow tide(HAGS). Remarks:Seewder P. dubia. Family Goniodorididae Genus Goniodoris Forbes & Goodsir, 1845 Gerns Limacia Miiller, 178 I

Goniodorisnodosa (Montagu 1808) Limacin clavigera Miiller, 1776) * CrabBay, 14.IX.1954,I specimen(IIJM); Crab No previous records from Skokholm. Crab Bay, 18.V.1969, 2 specimensin rockpool. Bay, 1990,2 specimens;Crab Bay, 1991,5 specimens;Hog Bay, 1991,I sPecimen Genus Ancula Lov6n, I 846 Habitat:In rock poolsunder stones at LWST.

Ancula gibbosa (Risso, 1818) Family Archidorididae Crab Bay, 24.III.I952,1 specimen(PDB). Genrs Archidoris Berch 1878

Family Polyceridae Archidorispseudoargus @app, 1827) Gerls Polycera Cuvier, l8l7 Crab Bay, 1948-197I,scarce; Hog Bay, 23- 30.VIII.1969, I specimen; South Haverl Poly c er a fa ero en si s Lemche,| 929 22.X.1957,a specimenof 2" (H.f-D; South No previousrecords from Skokholm.* Crab Haveq 23-30.VI[.1969,under overhangs on Bay, 1990,I specimen sponge(MJA); PetersBay, 1962,a maleand Habitat:Under stonein rockpool,lower littoral femalein copulationtogether with strips of zone. eggs;Peters Bay, 20.VII.I97I, I specimen North Haven,23-30.VI[.1969, I specimen Polyceraqu adrilineata (Miiller, 1776) (MJA); North Haven" 2.VIil.1969, I spe- SouthHave& 19.VII.1955, I specimenon weed cimen under overhang (HAGS); North (KST); South Haveq 17.VII.1966,7 spe- Haveq 20.VII.1971, 2 specimens(NDP). cimens on lower shore (HAGS); South Haven,7.VII.1968, I specimen(HAGS). * Family Kentrodorididae CrabBay, 1991,scarce; SouthHaver; 1991,4 Genrs Jorunna Berch, 1876 specimens;Peters Bay, 199I,4 specimens. Habitat:On rocksamong red algae in the lower Jorunnatommtosa (Cuvier, 1804) littoral zone. Crab Bay, 1960-1968,rare; North Haveq 2.VI[.1969, I specimen (MJA); South GenusPalio Gray, 1857 Haveq I2.VIlI.l969, I specimen(MJA).

Palio dubiq M.Sars, 1829) Family Facelinidae No previousrecords from Skokholm.* Crab GenvsFacelina Alder & Hancock 1855 Bay, 1990, 2 egg-layingspecimens; South Haverl 1990.2 eggJayingspecimens. Facelinqcoronda (Forbes& Goodsir,1839) Habitat:Under stones inpools inthe lowerlitto- There are only two known recordsfnom Skok- ral zone. holm.LittleBay, 16.VIII.1950, I specimenin Remarks: According to the InvertebrateCard rockpool at LWST;Little Bay,1S.VIII.1969, File Systemon Skokholm,P. dubia has not I specimenin rock facein shade. DEINSEAI, I994

Remarks:This specieshas neverbeen recorded Class Bivalvia from the localitieswe examined. Subclass Protobranchia Order Nuculoida Family Aeolidiidae Family Nuculidae Genx Aeolidia Cuvier, 1798 Genus Nncala l,amarc$ 1799

AeolfuIiapapillosa Q-iruneus,I 76I ) gdcula nucleus(Linnaeus, 1767) SouthHaver; 12.VIII.1969, I specimenin crack SouthHave4 3.VIII.1950,one valve (IIJMB & at low tide (MJA). * CrabBay, 1990,2 spe- UHW). * CrabBay, 1990-1991,ll valvesin cimens;Hog Bay, 1990,I specimen. shell-grit; North Haven, 1990, 5 valves in Habitat: In pools under stones,lower littoral shell-grit. zone. Subclass l,amellibranchia Gents A eoli di ella Berch. I 867 Order Taxodonta Family Arcidae Aeolidiellaglauca (Alder & Hancock,1845) Genuslrca Linnaeus. 1758 CrabBay, 22.VII.I955,1 specimenat low tide (KST). Ar ca tetra g ona Poli, l7 95 Accordingto Crothers(1966) I specimenwas SubclassPulmonala dredgedat 12 fathomsdept[ 100 yards off Order Basomnatophora North Point in 1960. Raven's Gully, Family Ellobiidae 25.VI[.1969,I live specimenonLithotham- Gents Leucophyda Winckworth, 1949 nioninapoolMJA). * NorthHaverq1990, I valvein shell-grit;Crab Bay, 1991,I valvein LeucophytiabfuIentata (Montagu, I 808) shell-grit. No previousrecords from Skokholm.* Crab Bay, 1990,4 specimens;South Haven, 1990, Family Glycymeridae I deadspecimen;HogBay, 1991, I specimen. Genus Glycymeris Da Costa, 1778 Habital Mid-littonl to LWST in dark.wet rock crevices. Glycy meris glycymeris (Linnaeus, I 758) No previousrecords from Skokholm.* North Gems Phyia Gray, 1828 Haveq 1990, I valve in shell-griq North Haven,1991, I valvein slrcll-grit. Phytia myosotis@raparnaud, I 80l) No previousrecords from Skokholm.* Crab OrderAnisomyaria Bay, 1991,1 specimenin shell-grit. FamilyMy'tilidae GentssRhomboidella Monterosato. 1884 Family Otinidae Genss Otina Gray, 1847 Rhomboidells prideauxi (Leacb I 815) No previous records from Skokholm and the Otinaovata (Browq 1827) Bristol ChannelArea. * NorthHaven.1990" I No previous records from Skokholm. South valvein shell-grit. Haven, 1990, commoq Hog Bay, 1990, scarce;Crab Bay, 1990,3 specimens;Peters GewsModiolus Lamarch 1799 Bay,1990, I specimen;HogBay, 1991, abundant. Modialus modialus (Lirrlaeus, 1758) Habitat:As L. bidentata SouthHaven, 2-I6.VI[.I969, occasionalsmall specimens(MJA). * NorthHaven, 1990, 1ju- venilevalve in shell-grit. SLIEKERet ol.: malacofaunaof Skokholmlsland

Modiolusbarbalus (Linnaeus, 1758) Genx Chlamys Roding, 1798 PetersBay, North Haven and South Haverl VIII.1969, occasiond specimens(Mln). * Chlomysvarin (Limneus,1758) PetersBay, 1991,scarce; Crab Bay, 1991,I Dredgedoffthe northcoast of Skokholmat 7-10 specimen;North Haver; 1991, I specimen; , fathoms(Crothers). Peters Bay, CrabBay and Hog Bay, 199I,2 specimens. / North HaverqVII-VI[-1950, I small valve Habitat:At LWM:rmong redalgae. I and fragments(IIJMB & IJHUD; Crab Bay, 14.IX.1954, I white juvenile specimen Modiolusphaseolinus @hilippi, I 844) (HItvt). + Crab Bay, 1991, 2 juvenile spe- Crothers(1966) claims this speciesdredged off cimers;North Haverl 1990-1991,8 valves in North Point at 12 fathomsdepth where it ap- shell-grit. pears to be abundant (1960). Crab Bay, Habitat:Under stones at LWST. 2.VIII.1950,smallvalves (HJMB & IJHW). GenusHinnites Defrance, 1821 GenusMusculus Riiding, 1798 Hinnitesdistortus (Da Costa,1778) Musculusdiscors (Linnaeus, 1758) No previousrecords from Skokholm.* Crab No previousrecords from Skokholm.* North Bay, 1991,4 valvesin shell-grit. Haveq 1990,3 valvesin shell-grit;Crab Bay, 199I, 2 specimens;Hog Bay, 1991,1 spe- Family Limidae cimeq North Haven,199I, I specimen GenvsMantellum Rii'ding, 1784 Habitat: At LWM amongred algae. Mantellumftrans (Gmelin, 1790) GanusMytilus Linnaets, 1758 StackBay, 30.VII.1963, I specimenunder hold- fastof Laminarla(RB SS). Mytilus eduEs Lirul.aleus,1758 Commonly distributed throughout the Skok- Family Anomiidae holm coastline according to records from Gents Anomia Linnaeus, 1758 1947-1969.We recordedthe speciesfrom all five localitiesinboth 1990and 1991. Anontia ephippiumLinnaeus, 1758 Remarks:Probably due to the large populations Peters Bay, 1I.MII.1949; Peters Bay, of breedinggulls on the island, only small l.VIII.1950 (HJIVIB& UHW); North Haverl specimenswere found. 29.VII.1950,common GIJNB & UHW); Crab Bay, 2.VI[.1950 (HJNA & UHW); Family Pectinidae CrabBay, l4.Ix.l954,frequent(HJM); South Genx Camptonectes MeeE 1864 Haveg North Haverq Hog Bay, 6- 13.Vrr.1968(HAGS). Camptonedestigrin us (Miiller, 1776) Remarks:Most likely the recordsof A. ephip- No previousrecords from Skokholm.* Crab pium from all five localities(1949-1969) Bay, 1991,I valvein shell-grit. representmisidentified H. squamu la.

Gewx Aequipeclen P.Fischer, 1887 Gents Heteranonla Winckworth. 1922

Aequipedenopercu laris (Linnaeus,1758) Hderanominsquamula (Linnaeus, 1758) Dredgedoff SkokholmIsland at 5-10 fathoms CrabBay, 2.VIII.1950 (HJMB & UHW);North (Crothers1966). One doubtful recordfrom Haveq 23.VII.1950,not uncommon(HJMB Peters Bay [Pectin chlamys (sic)], 2l.VI- & UHW). * CrabBay, 1990-1991,abundant; I.1955,I specimenat low tide(KST). * Crab HogBay, 1990,4 specimens, Hog Bay, 1991, Bay, 1991, 4 valves in shell-grit; North 3 specimens;South Haveq 1990, 4 spe- Haverl 1991,3valves in shell-grit. cimens;PetenBay, 1990,2specimens; Peters t- bl| hn DEINSEAI, I994 J Remarks:This specieshas neverbeen recorded Class Bivalvia from the localitieswe examined. Subclass hotobranchia I I Order Nuculoida FamilyAeolidiidae Family Nuculidae I j Gens Aeolidia Cuvier, 1198 GenrssNucula l-amarck- 1799 rl i Aeolidiapapillasa(Liruraeus, 1761) Naculo nucleus(Linnaeus, 1767) SouthHave4 l2.VI[. 1969,1 specimenin crack SouthHaveq 3.VI[.1950, onevalve G{JMB & * * at low tide (MJA). CrabBay, 1990,2 spe- [IHW). CrabQay, 1990-1991, ll valvesin cimens;Hog Bay, 1990,1 specimen. shell-grit; North H4verL 1990, 5 valves in Habitat:In pools under stones,lower littoral shell-grit. znne. Subclasst amellibranchia GenssAeolidiellaBerch, I 867 Order Taxodonla Family Arcidae AeolidieUaglauca (Alder & Hancock,1845) Gents Arca Linnaeus. 1758 CrabBay, 22.V1I.1955,1 specimen at low tide (KST). Arca tetragona P oli, l7 95 Accordingto Crothers(1966) I specimenwas SubclassPulmonala dredgedat 12 fathomsdepttq 100 yards off Order Basommatophora North Point in 1960. Raven's Gully, Family Ellobiidae 25.VItr.1969,I live specimenonLithotham- Gents Leucophyia Winckworth, 1949 nion inapol (MJA). * NorthHaverl 1990,I valvein shell-grit;Crab Bay, 1991,1 valvein Leucophytiabidentata (Montagu"1 808) shell-grit. No previousrecords from Skokholm.* Crab Bay,1990,4 specimens; SouthHaven, 1990, Farnily Glycymeridae I deadspecimen; Hog Bay, 1991,I specimen. Gents Glycymeris Da Costa, 1778 Habitat:Mid-littoral to LWST in dark,wet rock crevices. Gly cy m eris g Iy cym eris (Linnaeus,I 758) No previous recordsfrom Skokholm. * North GenusPhytia Gtuy,1828 Haven, 1990, I valve in shell-gri! North Haveq 1991,I valvein shell-grit. Phytia myosotis@raparnaud, I 80l) No previousrecords from Skokholm.* Crab OrderAnisomyaria Bay, 1991,I specimenin shell-grit. FamilyMytilidae GenvsRhomboidella Monterosato. I 884 Family Otinidae Genus Orina Gray, 1847 Rhomboidellaprideouxi (Leacb I 815) No previous records from Skokholm and the Otinaovata @rorvrl 1827) Bristol ChannelArea. * NorthHaven 1990.I No previous records from Skokholm. South valvein shell-grit. Haven, 1990, commoq Hog Bay, 1990, scarce;Crab Bay, 1990,3 specimens;Peters G enss M odi o lu s Lanarck, I7 99 Bay,1990, I specimen;HogBay, 1991, abundant. M odio Iu s modio lus (Limaeus, I 758) Habitat:As L. bidentata. SouthHaven, 2-l6.Vll[.l969, occasionalsmall specimens(MJA). * North Haven,1990, l ju- venilevalve in shell-grit.

q SLIEKERer ol: malacofaunaof Skokholmlsiand

Modiolus barbalzs (Linnaeus,1758) Genus ChLamysR0ding, 1798 Peten Bay, North Haven and South Haverl VIII.I969, occasiond specimens(MJA). '* Chlamysvarin (Lint:oLeus,1758) PetersBay, 1991,scarce; Crab Bay, 1991,I Drcdgedoffthe rprthcoastof Skokholmat7-10 specimeq North Haven, 1991, I specimen; fathoms(Crothers). Peten Bay, CrabBay and HogBay, 1991,2specimens. North Have4 VII-VIII-1950, I small valve Habitat At LWM amongred algae. and fragments(IIJMB & IJHW); Crab Bay, 14.IX.1954, 1 white juvenile specimen Modiolusphaseolinus @hilippi, I 844) (HJlvf). * Crab Bay, 1991, 2 juvenile spe- Crothen (1966) claims this speciesdredged off cimens,North Have4 1990-1991,8 valves in North Point at 12 fathomsdepth where it ap* shell-grit. pears to be abundant(1960). Crab Bay, Habitat Under stonesat LWST. 2.VI[.1950, smallvalves(HJMB & IIHUD. Genus .F/irnites Defrance, l82l Gert.x Musculus Roding, 1798 Hinnitesdistortus (Da Costa 1778) Musculusdiscors (Liruneus, 1758) No previous records from Skokholm. * Crab No previousrecords from Skokholm.* North Bay, 1991,4 valvesin shell-grit. Haverl 1990,3 valvesin shell-grit;Crab Bay, 199I, 2 specimens;Hog Bay, 1991,I spe- Family Limidae cimen;North Have4 1991,1 specimen Genrx Mantellum Rciding, 1784 Habitat:At LWM amongred algae. Mantellumhians (Gmelirl 1790) Genx Mytilus Linnaeus, 1758 StackBay, 30.VII.I 963,I specimenunder hold- fastof Laminarla(RB SS). My,tiluseduhs Linnaeus, 1758 Commonly distributed throughout the Skok- Family Anomiidae holm coastline according to records from GenvsAnomia Linnaeus, 1758 1947-1969.We recordedthe speciesfrom all five localitiesinboth 1990and 1991. Anomia ephtppiumLinnaeus, 1758 Remarks:Probably due to the large populations Peten Buy, 1I.MII.1949; Peters Bay, of breedinggulls on the island,only small 1.VI[.1950(HJMB & UHW); NorthHaverl specimenswere found. 29.VII.1950,common (IIJI\{B & UHW); Crab Bay, 2.VI[.1950 (]IJMB & UHW); Family Pectinidae CrabBay, 14.IX.1954,frequent (HJM); South Gerus Camptonectes Meek 1864 Haverl North Haveq Hog Buy, 6- 13.Vrr.1968(HAGS). Camptonedestigrinus (Miiller, 1776) Remarks:Most likely the recordsof A. ephip- No previous records from Skokholm. * Crab pium from all five localities (1949-1969\ Bay, 1991,I valvein shell-grit. representmisidentified H. squamula.

Gents Aequipe clen P.Fischer, I 887 GentssHeteranonia Winckworth- 1922

Aequipedm opercularis(Linnaeus, 1758) Hderanomiasquamula (Linnaeus, 1758) Drcdgedoff SkokholmIsland at 5-10 fathoms CrabBay, 2.V1I.1950(HJMB & UHW); North (Crothers1966). One doubtful recordfrom Haveq 23.VII.1950,not uncommon(HJMB PetersBay fPectin chlamys (sic)1,2l.VI- & UHW). * CrabBay, 1990-1991,abundant; I.1955,I specimenat low tide (KST). * Crab HogBay, L990,4 specimens; Hog Bay, 1991, Bay, 1991, 4 valves in shell-grit; North 3 specimens;South Have4 1990, 4 spe- Haveq 1991,3 valvesin shell-grit. cimers;Peters Bay, 1990,2specimens; Peten

il DEINSEAl, 1994

Bay, 1991, common;North Haven"1991, Family Cardiidae abundant.Valves are abundantin shell grit Gen:s P amicardinrn Monterosato, 1884 from both CrabBay (1991)and North Haven (1990and 1991). Purvicatdiumorale (Sowerby,184 l) Habital Under stonesat LWST. No previous records from Skokholm. * Crab Bay,.1991,valves scarce in shell-grit;North Order Eulamellibranchia HaveN990-1991, valvescommon in shell- Family Astartidae grit. Gems Godallia Turton, I 822 Panicardium exiguum(Gmelin, 179 1) Goodalliqbian gularis (Montagu,1803) Crab Bay, 2.VIU.1950, valves (HJMB & No previous records from Skokholm. * North uHw). Haven,1990-1991, valves, common in shell- grit. Genus Cerastoderma Mdrclr. 1853

Family l,eptonidae Cersstodermaedule (Lirnaeus, 1767) Genus lasaea Brown" 1827 SouthHaven" 3I.VII.1950, I freshlywashed up specimenG{JNB&UHW). L asae a r ub r a (Montagu, I 803) Crab Bay, 13.IX.1954,I specimencollected, Family Veneridae 'likely to be numerous'(HIM). * CrabBay, Gents GouMi a C.B.Adams, I 847 1990,3 specimens;Crab Bay, 1991, common; HogBay, 1990,4 specimens;Hog Bay, 1991, Gouldiqminima (Montagu,1803) scarce; South Haverl 1990, 2 specimens; No previous recordsfrom Skokholm. * North North Haveg 1991,3 specimens. Haveq 1990-1991,6 valves in shell-grit; Habitat: On rccks andunder stones among algae CrabBay, 1991,3 valvesin shell-grit. at LWM. Genrx Chione Megerle von Miihlfeld, l8l I G ents K eI I i a Turton. | 822 Chioneovata (Penmnt" 1777) Kelha suborbicularis (MontagU 1803) No previous recordsfrom Skokholm. * North No previous recordsfrom Skokholm.* Hog Haven,1990-1991, 8 valvesin shell-grit. Bay, 1990,2 live specimens;North Haven, 1990,2valves in shell-grit. Gents Venerupis t amarclg I 81 8 Habitat:Under stones at LWST. Vener u pispu ll a stra (Montagu,I 803) Gents Lepton Turton, 1822 No previousrecords fiom Skokholm.* Crab Bay, 1991,I deadspecimen; South Haveq Leptonnitidum TurtorU1822 1991,2dead specimens. No previous records from Skokholm and the Bristol ChannelArea. * NorthHaven 1991.2 Family Sanguinolariidae valvesin shell-grit. GenusPsammocola Blainville. 1824

Family Montacutidae Psammocola depressa (Pennant, 1777) Gents Mysella Angas, 1877 No previous records from Skokholm. * Crab Bay, 1991, I deadspecimen My sella bfuIentata(Montagu, I 803) No previous records from Skokholm. * North Haverl 1990,2valves in shell-grit.

@ SLIEKERet ol: malacofaunaof Skokholm lsland

Family Hiatellidae coNcLUstoNs GenusHiatella (Daudin in) Bosc, l80l In total, 114species of marinemolluscs are now recordedfrom Skokholm.Of this amounl 49 HfuteAaqrdica (Linnaeus,1767) specieswere newly recordedduring our survey. Variousrecords from all localitiesfrom 1949- Thefollowing specieswerc new recordsor new 1969.* Crab Bay, 1990,3 specimens;Crab live recordsfor the Bristol Chanrrl area (Sea- Bay, 1991,abundant; Hog Bay, 1990,I spe- war{ 1982& 1990):Skenea serpuloides, Ske- cimen; Hog Bay, 1991, I specimen;North nedt, n i t en s, Rho; mb oi de I I a pri deauxi atfr Lep ton HaverL1991, common nitidvm. Four of the earlier recordedspecies are Habitat Understonesor inLaminaria holdfasts probably based on misidentified specimens: AtLWST. Acanthochi tona fasci culari s, Hydrobia ulvae, Palio nothusandAnomia ephippium. Hiatella rugosa (Pennant,1777) As might be expectedfrom an island with a No previous records from Skokholm. * Crab rocky coastline,bivalves are poorly represented. Bay, 1990,l specimen. Eventhe few bivalvespecies inhabiting this type Habitat Boring in stoneat LWM. of ervironmentoccur in relativelysmall num- Remarks:H. rugosa is often consideredonly a ben. Althoughpredation by gulls wasregularly form of fL arctica.We prefertoretain its spe- observed,in our opinionthis carmotbe the sole cific status. causeof this phenomenon. Skokholmproves a suitablehabitat for opisto- branchmolluscs of which 18species are hitherto ClassCephalopoda recorded. Order Decapoda In our opinionthe rich gastropodfaunajustifies Family Sepiidae a marinereserve status for SkokholmIsland, and Genus ^SeplaLinnaeus, 1758 inclusion in the recently designatedSkomer MarineNature Reserve should be considered. Sepiaofricinalis Linnaeus, 1758 'borrcs' One record,2.VIII.1950, conceming 2 of this speciesby a gullery at BreadRock (HJMB & UHW). * No(h Haveq 1991,I ACKNO\^/LEDGEMENTS 'bone'. The authon would like to expresstheir gratitude to wardenMichael Betts andhis wife SusanBar- Order Octopoda clay for their hospitalityand inspiringenthusi- Family Octopodidae asm during the visits to Skokholm Island, as Genus Eledone Lnacll 18 17 well asto the Dyfed Wildlife Trustfor enabling us to conductour malacologicalsurvey. Ac- Eledone cirrhosa (Lamarck,I 798) knowledgementsarc also due to Mr. J. Goud NorthHaver! 20.IX.1955, I specimencaught by (Nationaal NatuurhistorischMuseunl Leideq a limpet and held to the rock surfaceby orrc The Netherlands)for the SEM photographsused tentacle. The animal was releasedand kept in this paper,as well as to Mrs. J. Light (Go- alive for severaldays. dalming,Surrey, England) and Michael Bettsfor critically readingthe text. We also like to thank Mr. H.P.M.G.Menkhont (NatuurmuseumRot- terdanL The Netherlands)for identification of severalmicromolluscs.

E DETNSEAl, 1994

REFERENCES - Crothers, J.H., 1966 - Dale Fort Marine Fauna - Supplement Seaward,D.R., 190 Distribution ofthe marine molluscs of west Europe - Conservanry Council. Peter' to Field Studies 2 north \ature\ Fretter, V. & A. Graham, 1977 -'Ilne prosobranch molluscs borough \ of Britain and Denmark, Part 2 - Trochace4 Supplement Stanbury,D.J., 1974 - Some marking e4perimentson a 3 - The Joumal of Molluscan Studies 8l-87. population of Monodonta kneata (Da Costa), South Graharn, A., 1988 - Synopses of the British Fauna No.2; Haven, Skokholnr, Pembrokeshire- Skokholm Bird Molluscs: Prosobranch and Plramidellid Gastropods - ObservatoryRepott 1974: 27-3 4. l,ondon. Tebble,N., 1975- Britishbivalve seashells. A handbookfor Jones, A.M. & J.M. Baxter, 1987 - Synopsesof the British identificalion- london. Fauna No.37; Molluscs: Caudofoveata" Solenogastres, Thompson,T.E., 1988- Synopsesof the BritishFauna No.8; Polyplacophoraand Scaphopoda- London Molluscs:Benthic Opisthobranchs (Mollusca: Gastro' Seaward,D.R., 1982 - Sea area atlas ofthe marine molluscs poda)- Leiden. of Britain and lreland.- Nature Conservancy Council. Shrewsbury received27 Oclober 1992 acceotedl5 December1992 updatedl2 October1993

PLATE I (scalebars are loo mu) Figure I Skeneoserpuloides (Montagu, lB0B), Skokholm lsl., North Haven,FJAS 4923; Figure 2 Skeneonitens (Philippi, lB44), Skokholm lsl., Nofth Haven,FjAS 4922; Figure 3 Rissoe/lodiophono (Alder, lB4B), Skokholm lsl., Hog Bay,FJAS 6597; Figure 4 Aperturewith operculum,same species as Fig.3; Figure 5 Brochystomio/ukrsi (Jeffreys, lB5B), Skokholm lsl., Hog Bay,FJAS 6601; Flgure 6 Aperturewith operculum,same specimen as Fig.S; (FJAS= collectionF.J.A. Slieker, Schiedam) SLIEKERet o/.:ma.lacofauna of Skokholmlsland

PLATE I