MARINEMOLLUSCSOFMAYOR ISLAND EN M Llligan . Most of The
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127. MARINE MOLLUSCS OF MAYOR ISLAND E.N. Mllligan. Most of the collecting was from open rock and sheltered reef habitats (large stones and boulders). Although sandy beaches were present at Opo, Omapu and Orira (N.W.Bay), they appeared to be too steep for colonization by sand flat molluscs. Some sublittoral species which encroach into the tidal zone on sand flats were found Yi/ashed up on the beach, e.g. Barysplra spp. Omapu Bay was more exposed than Opo, and in • the former a good deal of sand occurred with the stones where collect• ing was done. Opo Bay supplied more typical sheltered reef condit• ions with large immovable rock blocks rising from below extreme low tide, and with smaller stones amongst them which at low tide were generally free from sand, Collecting was not primarily for compiling a species list. Doubtless a few common species widespread in dist• ribution were not collected or recorded for inclusion, e.g. Melag- raphia, Nerita9 Siphonaria. Eighty species were recorded, - the number being increased by 14 specimens, in drift. Some are from shallow water, but others are deep water or pelagic, These latter two are characteristic of exposed coasts and islands where the land shelves deeply off-shore. Besides these there is the record of 4 Cephalopods, 3 of which are rather rare on our coasts, ' Spirula spirula, the common white ram's horn•shell, has been found to live in depths between 110 fathoms to 1,100 fathoms. One, specimen of Tethys tryoni was found washed up but none were•found in pools. This evidently was not the season for these annual tectibranchs to come into shallow water to breed. The specimen found was purplish and not the brown colour of specimens found in pools. The purplish colour appears to be characteristic of this mollusc- during its off• shore phase. Of interest also were two species, Notosinister in- felix and Joculator dirempus9 originally found alive only by dredging, which were found living in Microdictyon in a deep high-tidal pool* Washings from this algae produced the large number of 24 species. In the following lists numbers 'following the species are those- in the check lists of Powell (1946 and 1.953). Saxostrea is a synonym of Crassostrea (Thomson ~ 1954). + Denotes found on more than one of the' islands. * Denotes found on all three. 128. PELECYPODA Philobryidae: +Hochstetteria munita 43-1 spec., high tide pool, Opo. Cosa filholi 48-1 spec., in drift, Opo Bay. Mytilidae: - " »Trichomusjculus barbatus 68—low tide crevices,-Opo, Omapu, Ostreidae: -.- *Crass6strea glomerata 100.-more sheltered rock shelves, "': ":A^-i-Opo Bay. Carditidae: +Cardita- aoteana 1,29- - 1 juvenile valve,'.drift,.- Opo. Leptonidae: +Lasāea maoria 1 66 .-' high tide-muddy crevices., N. arm, Opo. +L. hi nemo a i 67 -• dead shells,. drift, Opo. .ii.-. +Notolepton sanguineum 197 - ditto.. +N. citrihum 198 - Ditto. Veneridae: —...vv +Tawera spissa 251 - dead shells, drift, Opo. Chione (Austrovenus) stutchburyi 2!i>7 - ditto. Hiatellidae: •fHiatella australis 273 - common in low tide crevices and • under stones, Opo. < G A S T> E- R 0 P 0 D A Scissurellidae: +Scissurona rosea 305 - common, high tide pools, Opo. Haliotiidae: t ' ' *Haliotis (Paua) iris 313 - common on rocks, S.Opo Bay. Fissurellidae^: r -; Incisura lytteltonensis 318 - common, low tide seaweed • washings, Omapu Bay;.high tide pool, Opo. ^Tugali suteri bascauda. 325 common under-; low tide rocks, Opo Bay. r , Trochidae.: •'' •••-V:-'••' ^^"''^'^;-:^--'• . r, , ;' »Thoristella oppressa- 346 - -common on low tide' seaweed/ '.. : Opo and Omapu.; : ,- .., ' ": Paraclanculus peccatus 349 - 1 spec, of this rare mollusc found in seaweed drift, Omapu, by E.l/hite. *Anisodiloma lugubrls 360..- low tide "under smooth stones,Opo. Cantharidus purpuratus 364 - 1 spec. , Opo drift. (pu. Micrelenchus tenebrosus 373 - 2 spec.-, low tide stones,0ma- *M. dilatatus 377 - common on low tide seaweed, Opo. 129. Cantharidella tesselata 379 - common on low tide seaweed,Opo. +Fossarina rimata 380 - few specimens in high tide crevices, North Opo. Stomatellidae: -'"Herpetapoma bella 381- - common under stones, low tide, Opo. Liotiidae: -*"Liotella polypleura 429 - common, high tide pool, Opo. Turbinidae: '•'Lunella smaragda 488 - common on stones & weed, low tide,Opo. Patelloididae: »Notoacmea pileopsis 509 - abundant, high tide, exposed rock. +N. pileopsis cellanoides 51 9 - not common as last but on rough surfaces or head of washes. N. subtllis 514 - 1 spec, of this deepwater sp., drift, Opo. *Atalacmea fragilis 521 - common under smooth stones, Opo. Patellidae: ^Cellana radians 523 - common on rock raid-low tide. Wide variation in this spec. Some high apex length 45 mm. x height 13 mm. +0. stellifera 526 - 1 spec., low tide rock, Omapu. C. denticulata 528 - 3 spec, of this common southern limpet on vertical exposed rock. *C. ornata 529 - as C. radians but on rough surfaces and extending rather further up shore. Littorinidae: •Melaraphe oliveri 551 - abundant all rock in high tide -^d ^ splash zones. Zelaxitas cystophora 558 - fairly common, seaweed was' Omapu. / Z. miera 559 - common, high tide pool, Opo. Bembiciidae: +Risellopsis varia 563 - high tide crevices •=> N. Opc 0 Rissoidae: +Estea semiplicata 598 - common in high tide pool,/^ E, nov. sp. cf. minor 600 - not common in high ti?z, N. Opo. (Type locality, Tauranga.^ ^Haurakia hamiltoni 616 - not uncommon, seaweed w° Omapu and Opo* . +Merelina lyalliana 625 common understones in , ditions just below mean low watf Merelina superba? 631 - 1 spec., ditto, Promerelina lacunosa 642 - 2 spec., high tide Notosetia infecta 667 - 1 spec- on sponge, lo North Opo. ( • +N. mi cans 671 - few spec, pool drift, North 0], o N. subcarinata 686 - uncommon, high tide pool, e5 if Scrobs semen 700 - uncommon, seaweed washings, h& § high tide pool, Opo. ^ *Dardanula olivacea 708 - common,, low tide, stones and weed, Opo and Omapu. 130. Dardanula limbata 711 -2 spec, high tide pool, Opo. Rissoinidae: +Rissoina chathamensis 729 - not common, low tide pool and drift, Opo. — +R. rufolactea 736 - 2 spec., pools, North Opo. Cerithidae: +Zeacumantus subcarinatus 760 - common high tide pools, North Opo. +Joculator dirempus 787 - not common, on Microdictyoh in large, deep high tidal pool, North Opo. Vermetidae: Novastoa lamellosum 801 - low tide, Opo. Triphoridae: +Notosinister infel.ix 794 - on Microdictyon, deep, high tidaT pool, North Opo. Turritellidae: Zeaculpus fulminatus 813 - dead shells not uncommon, Omapu. Calyptraeidae: Maoricrypta (Zeacrypta) monoxyla 829 - common, low tide,Opo, Cymatidae: Mayena australasiana 869 - 2 specimens, low tide rocks, south Opo. Janthidae: Janthina (iodina) exigua 866 - dead shells, drift, Opo. Cominellidae: Cominella maculosa 1103-- 1 spec, low tide rocks, S.Opo. Muricidae: Zeatrophon ambiguus 1132 - 1 spec., dead drift, Omapu. Thaisidae: ^Neothais (Dicathais) scalaris 1163 - common low tide ledges and niches, rocks. ^Lepsiella scobina (albomarginata?) 1165 - common, inter- tidal rocks. Olividae: Baryspira australis 1238 - few dead shells, hermit crabs, Omapu. B. (Alocospira) novae zelandiae 1240 - ditto. B. (Pinguispira) depressa' 1 241 - ditto. Turridae: Antimelatoma buchanani maorum 1282 - 1 spec, of this deep water species washed up, Opo. Terebridae: Pervicacia tristis 1346 - uncommon, hermit crabs, Omapu. Aplysiidae: Tethys tryoni 1400 - 1 spec, washed up, Omapu. 131 * Doridigitatidae; +Allolpdori ? 1423 - 1 spec*, low tide pool,N.Opo. Ellobiidae: *Leueono.psis obsoleta 1454 - high tide crevices, N.Opo, ^uīīeommon, A M P H ī N E U R A Lepidochitonidae.s. Paricoplax croclna 1771 - low tide pool, N. Opo. Gryptoconchidae: »Acanthochiton zelandicus• hooker! 1779 - ditto (7 valves)'. , Chitonidae: *Sypharochiton sin.clairl (Gray) 1810 - Midlittoral, common. CEPHALOPODA Spirulidae: - Spirula spirilla 1826 - drift, Opo. Ommastrephidae: NotoAQ^a£ug_ 1831 ~ 1 spec, washed up, N.W. Bay; 1 spec at Omapu, Octopodidae? ' *Qc^QP^.:5!..,"15?.1!1^ 1.845 ~ 1 spec , approx. 90 cms. under boulder, S-Opo reef. Argonautidae: *Argcnautanodosa ••- about 10 female specimens found, all but '"1852""'C'...ree 1 in, or less, about 8 cms.. One from ' N.W. Bay, 2 from Omapu, Most small ones from Omapu- 2 each from N.W. & Opo Bays. This mollusc is commonly found on the Island at this time of the year, evidently in shallow water while breeding. Perhaps seasonable weather accounted for their rarity on this occasion, However, many hundreds of the in conspicuous male were found washed up„ Opo Ba; 32. MARINE MOLLUSCS OP HEN ISLAND. E.N. Milligan, The area studied was limited to Old Woman's Cove which included dissected headland and sheltered rocks and boul• ders. Collecting was concentrated on the rock and boulder comm• unities for the purpose of making comparisons with equivalent comm• unities occurring at Little Bj.rrier and Mayor Is. Open rock usually shows a characteristic fauna for one province and this is probably due to the high degree of specialisation required in a more unfav• ourable environment. The greater variety of more favourable con• ditions among sheltered rocks allow ready colonisation by a variety of species and consequently comparisons within a single province can be more readily made in this habitat. At the head of Old Woman's Cove the rough stones and boulders were lying in sand from neap to higher tide levels. At neap tide the undersides of these stones were covered with large numbers of the Rissoid Merelina lyalliana and less comm• only with the bivalves Hochstetteria munita and Trichomuscuius bar- batus. Merelina was found occurring in the same manner on the sandy Omapu Bay stones of Mayor Is. but apparently without the other two species. At low tide spring the sand level dropped \ and the rocks were piled on one another, and covered with a e^" ^ pj\ uous mass of sponge and .ascidians. It was from here that ^$\o *A the records, came, ' o ®Y* %\ The following list (67 spp. and SL ^laV**?^ refers to species found in the Cove unless otherwise stated, '^©V* A — ————— %\ $ P S L Y C OP 0 D A %K< Arcidae* Area nc vaeze ?•::•&-• -t 1 ae .-.