III.—On the Mollusca of the Crag-Formation of Iceland

Dr. 0. A. L. Morch—On the Crag of Iceland. 391 formed in strata incapable of being stretched, which occur among strata capable of being stretched by the weight of a mass of rock displaced by a fault. Fig. 2 is intended to show two wants, amount- ing together to about 73 yards, caused by the fault above mentioned, which had a maximum downthrow of 220 yards; its zero points being one mile distant. It is by no means asserted that even in the case of shales the capa- bility of being stretched is without limit In every case after the limit is reached, the fault can only increase its downthrow by in- creasing in horizontal length (i.e. adding to the distance between its two zero points), or by producing on its downthrow side one or more faults along lines of weakness forming angles with its own line. Such lines of weakness, destined to become faults, will be found in the largest wants in the thickest strata. Faults which disturb stratified deposits of varying composition are very frequently filled with a "hash" of the softer strata only, such as shales and fire- clays ; and this circumstance may be due in some cases to the fact that the fault has been made (during the increase of a master-fault) along a line from which the harder beds—of sandstone or the like— had been previously withdrawn. When a master-fault, after exhausting the capability of being stretched possessed by the strata displaced, produces smaller faults, the latter will have their downthrow on the side towards which the master-fault increases. The superincumbent strata will settle down along the lines of the master and smaller faults till the gap which would otherwise have existed is filled up.

III.—ON THE MOLLUSCA OF THE CRAG-FOBMATION OF ICELAND. By Dr. 0. A. L. MOKCH, For. M. E. Soc, Edin.; Pot. Corr. Z. 8., Lond.; Acad. Sc, Philad. HE fossils of the volcanic Islands of the Atlantic Ocean, St. Helena, • Madeira, Teneriffe, and Iceland, have a special interest, as giving Tdates relative to the supposed Atlantic Continent. The fossil land-shells of St. Helena and Madeira appear to belong to a period corresponding to the Crag-formation of England. The marine fossils of the Canaries, on the contrary, belong to a somewhat more ancient period. In Iceland beds of fossils are found in several places, but belong- ing to very different geological ages. The most celebrated forma- tion is the Surturbrand, containing a fossil flora, chiefly known from the description of Prof. 0. Heer of Zurich, from the collections of Prof. Steenstrup, etc. It contains about thirty-seven species of plants, chiefly belonging to Araucarites (A. Sternbergi, with stems from 1^ to %\ feet in thickness), Betula, Gorylus, Alnus, Vitis, Lyrio- dendron, Ulmus, Bhamnus, Bhus, Quercus, etc. A wing of a Carabus is the only trace of animals. The author considers this formation to be of Miocene age, but belonging to two different periods. The fossil shells belong to a more recent period; but as they are never found in the same place in superposed strata, it is difficult to 392 Dr. 0. A. L. Morch—On the Crag of Iceland. indicate their relative age with security. From zoological reasons it is however evident that some of the beds are of a more recent date; whilst others, especially the beds of Husavik Hallbjornastadir- camb,1 the best-known formation, is the oldest, and probably cor- responds to the older .Crag of England and Belgium. The following authors have contributed to the investigation of this subject:— 1. Eggert Olafssen og Biarne Pavelsen. Eeise igjennem Island, 1752-57. Soro, 1772.—In vol. i., pp. 126 and 153, is described a layer of fossils in bluish clay, 7 to 10 feet thick, in the border of the Leyraa and Laxaa (two rivers), containing Peeten Islandicus, L., with the colours well preserved, and Oyprina Islandica, L.—In vol. i., p. 410, it is stated that fossil shells are found in several localities in Bardestrands and Isefjords Sysseler, close by the shore, from be- tween one and two to four fathoms above high-water mark, and in several other places in South Iceland, but not afterwards investigated, so far as I know. It is mentioned that near many of the houses are found large heaps (middings) of shells of Oyprina and Mya, eaten by the in- habitants, but which are not to be mistaken for fossils, any more than are the shells and sea-urchins the ravens have left on the rocks far inland.— In vol. ii., p. 936, several localities for fossil shells are mentioned, on the authority of the inhabitants. A hill close to Soget contains shells in a bluish very soft stone, which are washed out by this rivulet, viz., Cardium Islandicum, Oyprina Islandica, and especially Tellina calcarea, Chem. At another place, in a very hard rock, is found Peeten Islandicus, with the colours of the shell preserved. All these localities seem only to yield shells exactly like those now living • on the coast of Iceland. The following locality contains the greatest number of shells, many of which differ from those now living in the seas of Iceland.—Vol. ii. p. 665. Fossil and partly mineralized (crystal- lized) shells are found in a hill called Hallbjornastade-Kamb, 140 feet high, situated close by the shore, in the vicinity of Husavig harbour, on the Eastern part of the North coast of Iceland. The mineralized (crystallized) shells are only found on one spot; they are mostly shells of Cardium, Venus (Cyprina). The following shells are in- dicated : a. Astarte; b. Cardium ciliatum ?; c. Peeten Islandicus; d. Mya truncata; e. Buccinum undatum ; f. Littorina; g. Fusus Olavii, Beck ; h. Natica clausa, and perhaps N. aperta, Loven. 2. Olaus Olavius. CEconomisk Reise igjennem de nordvestlige, etc. Kanter af Island. 1780.—In vol. ii. p. 572, is a plate with shells from Halbjarnastadirkamp. The figures are very bad, but the plate gives a very good idea of the abundance and position of the fossils. Tellina, Cyrtodaria, Nassa, Trophon, Pleurotoma, Natica, Bittium ? The best figure represents an Astarte, very like to A. castanea, Say. 3. Voyage en Islande et aux Gronland, execute pendant les annees 1835 et 1836, sur la corvette la Recherche, commande par M. 1 " HaUbjmnarstada-Kamb " is the official way of spelling this locality, but the various authors referred to wrote more or less in Danish or old Icelandic; this will sufficiently explain the diversity in writing this name in the various works here quoted.—0. A. L. M. Dr. 0. A. L. Morch—On the Crag of Iceland. 393 Trehouart, publie sous la direction de Mr. Paul Gaimard. Mineralogie et Geologie, par E. Eobert. 1840.—P. 283, " Les coquilles fossiles de Husavik Hallbjarnastadarkambur sont d'une abondance extreme dans ce terrain, et admirablement conservees, ce sont d'apres Mr. Deshayes, qui a constate leur identite avec celles qui vivent encore dans ces memes lieux, notamment les Cyprina Islandica, Mya arenaria, Tellina solidula (T. ovata, Sowb. ?), Tellina tennis (probably T. cal- carea, Oh.), Natica clausa, Cardium voisin de ciliatum, Solen vagina, S. ensis ? Buccinwm voisin de Buc. reticulatum." It is stated that the great specimens of Oyprina contain chambers filled with a blackish matter, probably being part of the animal (perhaps the stomach). " Au dessus de ce gissement, les coquilles sont entassees pele mele comme dans un falun; le tufa se divise alors en plaque et renferment principalement des petites bivalves." Mr. Eobert figures as Oyprina Gaimardi a shell which Mr. Deshayes considers a very inflated variety of Cyprina Islandica, L. 4. G. G. Winkler. Island der Bau seiner Gebirge und dessen geologische Bedeutung. Miinchen, 1863.—The fossils of Hallb- jarnarstadir are for the first time stated to belong to the Crag-forma- tion. Twenty-seven species are enumerated. Through the favour of the author, I have received some sketches of the new species, which enable me to give the following observations:—Tapes virginea, Forb., is Tellina calcarea, Ch.; Astarte Hjaltalini, Winkl., is, as the the author himself supposes, A. crebricosta, Forb.; Natica Steens- trupiana, Winkl., is Natica aperta, Loven.; Planorbis spirorbis, Miill.,1 is probably mis-written for Spirorbis borealis, Daudin; Patella leevis, Winkl., appears not to differ from Patella pellucida, L., Gyrtodaria Heerii, Winkl., is perhaps G. angustata, Nyst. The fol- lowing true Crag-fossils are named:—Oyprina rustica, Sowb.; Tellina ovata, Sowb.; . Gorbulomya complanata, Sowb.; Gyrtodaria siliqua, Spgl.; Natica varians, Duj.; Natica Tiemiclausa, Sowb.; N. occlusa, Wood. At p. 211 the following species are named as occurring at Fossvogur, which may be considered of a more recent period:— Mya truncata, L.; Buccinwm undatwm, L., var. vulgatwm ; Balanus, sp.; Tellina, sp. From Arnabauli, p. 212, which appears to belong to the same period :— Cyprina Islandica, L.; Astarte borealis, Chem.; Mya truncata, L.; Pholas crispata, L.; Pecten Islandicus, L.; Buccinwm undatum, L., var. vulgatum. 5. G. W. Payhull. Bidrag till Kannedommen om Islands Bergs- bygnad. (Kgl. svenska vetenskaps Akademiens Handlingar. 7 Band. 1867. Stockholm.) At p. 47%is given by the late author a descrip- tion of the fossiliferous layers of Hallbjamastada, and at p. 49 a list of species named by the present author.2 The specimens are partly in the Museum of Copenhagen, partly in Stockholm. At p. 48 the layer of Fossvogur, between Eeykiavik and Hafnarfjord, is more specially described. It contains—Saxicava rugosa, L.; Mya trun- cata, L.; Tellina sabulosa, Spgl. (T. calcarea, Ch.); Nucula tennis, Mtg.; Balanus, sp. These species indicate a more recent period 1 Wood, 1848, p. 9, tab. 1, fig. 11. 3 Quoted in the Catalogue as Morch-Paykull's List. 394 Dr. 0. A. L. Morch—On the Crag of Iceland. than the Crag. The Crag is not found in Greenland, but a formation probably corresponding to the layers of Fossvogur and Amabauli. In the following paper I have given a list of thirteen species of shells from Pattorfik, in the Omenaksfjorden. They are still living in the seas of Greenland, except Cyrtodaria siliqua, Spgl., a Newfoundland species, and Panomya Norvegica, Spgl. (the form P. arctica, Lam.), found on the north coast of Iceland, and in the Cattegat. 6. H. Rink. Om den geographiske Beskaffenhed af de danske Handelsdistrikter i Nordgrdnland tilligemed en Udsigt over Nord- gronlands Geognosie, 1852. (Kgl. danske Videnskabernes Selskabs Skrifter, 5 Easkke, 3 Bind.) The Crag-formation of Hallbjarnastadir is characterized by the fol- lowing fossils:—1. Species not found living but fossil in England and Belgium:—Corbulomya, two or three species; Actaon Noes, Sowb.; Natica varians, Duj.; JV. hemiclausa, Sowb.; N. occlusa, Wood; IAttorina littorea, the Crag variety, Buccinopsis crassum, Nyst.; Nassa monensis, Forb. ?; Voluta, sp.; Trochus, two sp.; Cyrtodaria Heerii, Winkl.; Mactra, two or three sp.; Tellina obliqua, Sowb.; Tellina prcetenuis, Leathes ; Cyprina Oaimardi, Eobert; G. rustica, Sowb.; C. Islandica, L., var. pumilio ; Mytilus hesperiantts, Lam. 2. The following species are found living in the arctic regions, and are found fossil in the Crag of England: Natica Oroenlandica, Beck ; N. clausa, Sowb.; Tritonium Grcenlandicum, Ghem.; Tr. undatum, var. pumilio; Fususpropinquus, Aid.; Fusus fornicatus, Fabr.; Pleurotoma twrricvla, Mtg. (but very large) ; PI. rufa, Mtg.; PI. Treveylliana, Turt.; Admete viridula, Fabr.; Patella pellucida, L.; Teredo, sp.; Solen siliqua, L.; S. ensis, L.; Saxicava Norvegica, Spgl.; Oyrtodaria siliqua, Spgl.; Mya truncata, L.; M. arenaria, L.; Tellina calcarea, Chem.; Cyprina Islandica, L.; Astarte crebricosta, Forb.; A. com- pressa, L.; Cardium Grcenlandicum, Chem.; Modiolaria nigra, Gray; Mytilus edulis, L.; Cardium echinatum, L. The following species only are found living: Acrybia lutea, Gould ; IAttorina Grcenlandica, Chem.; Tritonium Tottenii; Tritonium scalari- forme, Beck. At present the north coast of Iceland is quite arctic, but in the Crag-period the temperature must have been much milder, at least as at present on the west coast by Eeikiavik. The following genera, which indicate a southern climate, are still found on the west coast of Iceland: Actmon, Trochus, Patina, Nassa, Mactra (elliptica), none of which are arctic; IAttorina littorea, Solen ensis, S. siliqua, Cardium echinatum, none of which are arctic shells, have not been yet discovered in Iceland, but may possibly be found there hereafter. The change of the climate of the north coast of Iceland to one of a true arctic nature probably has resulted from an elevation of the land in that part which prevented the free passage northwards of the great equatorial current. Natica aperta is considered by Prof. C. Mayer to be a tropical form, but this species is, on the contrary, a true Glacial form. Prof. Winkler believes that the dwarf variety of Cyprina Islandica Dr. 0. A. L. Morch—On the Crag of Iceland. 395 indicates a warmer climate, like that of the Baltic near the coast of Mecklenburg, where a small variety is said to exist. The size of the specimens of the Crag-formation of Iceland is in general not remarkable, except the following species, which may be considered dwarf varieties: Fusus Olavii (perhaps dwarf variety of F. gracilis), Oyprina Islandica pwmilio, Cardium Gromlandicum, Tritonium Grosn- landicum, Ch., Tritonium undatum pumilio. The following species may be considered very large in the Crag- formation of Iceland: Actmon Norn, Natica aperta, Pleurotoma turricula, Corbulomya, two or three species, much larger than any specimen known to me from England. The three species of Mactra may be considered large in comparison with the species now living in the North Sea. The dwarfed condition of certain species may depend on various causes. The North Sea shells all become smaller when they enter the Cattegat and the Baltic, diminishing in size according to the decrease of the saltness of the water. The freshwater shells, as Neritina and Lymneea, decrease, on the contrary, in the same pro- portion as the water becomes salter. List of Mollueca found in the Crag-formation of Iceland at' Hallbjarnastadir. (The species marked with * are not known to me fromautopsy) . 1. Actmon Nom, Sowb., Min. Conch., tab. 374. Tornatella Noee, Nyst, Coq. Foss. de Belgique, p. 424, tab. 37, fig. 22. One specimen 16 mm. long, and 10 mm. in diameter ; and another smaller : Suturis depressis, subcanaliculatis, labro intus sulcato. 2. Acrybia lutea, Gould. Natica aperta, Loven. Natica Steenslrupiana, Winkler, I.e. p. 209. Bttlbus apertus, Loven, Mdrch, apud Paykull. Tungabakker Tjornaes. The largest specimen is 32 mm. long and 25 mm. in diameter. • 3. Natica (Lunatia) Groenlandica, Beck. Natica catena, D. Costa, Wood, Winkler, p. 208. Mamma et Lunatia Grcenlandica, Mbrch, apud Pajrk. Common (Winkler, Paykull). *4. Natica (Lunatia) varians, Dujardin. Natica varians, Wood, p. 142, tab. xvi., fig. 6. Natica borealis, Gray ? Two specimens; 30 mm. long, 25 mm. in diameter; aperture, 21 mm. long, 13 mm. in diameter. *5. Natica (Zunatia?) Jiemiclausa, Sowb., tab. 479, fig. 2. Natica hemiclausa, Winkler, I.e. p. 209. Bare (Winkler). •6. Natica occlusa, Winkler. Natica occlusa, Winkler. Common (Winkler). 7. Natica clauea, Sowb. Natica clausa, Sowb., Winkler, p. 209, w. 5, Mbrch, Payt. Common (Winkler, Paykull.) 8. Natica (Neverita ?). One specimen, 29 mm. long, 25 mm. in diameter; aperture, 20mm. Perhaps the N. hemidausa of Winkler. 396 Dr. 0. A. L. March—On the Crag of Iceland. *8. IAttorina littorea, Linn. Zitorina littorea, L., Wood, p. 118, tab. x. fig. 14. One specimen exactly corresponding to the variety figured by Wood, smooth and banded; 16 mm. long, circ. 15 mm. in diameter. Paytull. 9. IAttorina Grcenlandica, Chem. The nucleus of some specimens. (Gudman.) 10. Tritonium Tottenii, Stimpson. Buccinum undatum vulgatum, Wood, tab. 3, fig. 12c. „ „ Winkler, p. 210. Probably only a variety of Buccinum undulatum, Moller. 11. Tritonium Grcenlandicum, Chem. Buccinum undatum, var. lamusculum, Wood, p. Ill, tab. Sf, fig. 12a. Tritonium undulatum var. (traenlandicum, MSrch, Payk. Fragmentum T. Imvis, with the epidermis; 20 mm. in diameter, from Paykull. This species is mostly a dwarf variety of the preceding. 12. Tritonium undalum, L. (var. pwmilio). circ. 36 mm. long; 20 mm. in diameter, plicisobliquis suturalibus prominentibus. Three specimens. 13. Tritonium scalariforme, Beck. circ. 25 mm. long.; 12 mm. in diameter; 13 mm. long spirse. One specimen, Gudman. 14:. Buccinopsis crassa, Nyst. Buccinum crassum, Nyst, p. 569, tab. 44, fig. 7. Buccinum Dalei, Sowb. M.C., tab. 488, fig. 12 ? Buccinopsis Dalei, Sowb., var. Morch, Payk. One specimen measures 39 mm. in length, and 20 in diameter. Several specimens from Gudman and Paykull. It reminds one of a dwarf thick-shelled Fusus aniiquus. 16. Fusus (Sipho) Olavii, Beck.1 Testa Fus. gracili affinis sed parva tenuiuscula, sutura profunda, spira abbreviata. Mammilla apicalis obliqua Littorinain obtusatam non absimilis. Long, speciminis majoris, 35 mm., diam. 17 mm. Long, speciminis minoris, 16 mm., diam. 9 mm. Fusus gracilit, Wood, var. a, tab. vi. fig. 10a, non absimilie. Fusus Olavii, Beck, Morch, apud Payk. Var. Spira longa, 38 mm. long, 16 mm. in diameter. Trophon gracilis, Wood, tab. vi., fig. 106.; var. /8 non absimilis. 17 Fusus (Sipho?) propinquus, Alder; var. Spira elongate. Fususpropinquus, Aid., Morch, Payk. Among Paykull's collection, now in the museum of Stockholm, I believe there is a specimen of this species. It is certainly found in the Crag of Belgium. I have seen several specimens, with well-preserved apices, corresponding in shape to the figure given by Nyst. 18. Fusus (Neptunea) fornicatus, Fabr. Fusus aniiquus, Wood., tab. xi. fig. 4a-* (Winkl.). Fusus despectus, L., var. Morch, Payk. Common (Winkler). I have only seen a well-preserved fragment, 43 mm. in diameter. 1 Not the Fusus Olavii, Beck, in Eiciwald Urwelt Rnsslands, 1842, p. 141. Dr. 0. A. L. Moreh—On the Crag of Iceland. 397 20. Nassa monensis, Forb., Jeffr., verbotinus. Testa conioa, anfr. planiusculis conferte costatis; costse oirciter 29 in anfr. ultimo, bifidse obsoletse arcuate; spiraliter lirate unde interstitiis costarum foveolatis. Long. 12 mm., diam. 5^ mm.; spiras 7 mm. long. Nassa labrosa, Wood, tab. 3, fig. 8, quoad formam sed non sculptura. Nassa Cuvieri, Payr. non absimilis. I have compared four specimens from Mr. Gudman, and from Spengler's collection one specimen. I consider it very different from N. monensis, Forb., which I," however, do not know from autopsy. 21. Pleurotoma (Ischnula) turricula, Mtg. Clavatula turrieulq, Wood, tab. viii., fig. 13, Winkler, p. 211. Very large specimens, 20 mm. long, 8 mm. in diameter; spirae, 10 mm. 22. Pleurotoma (Ischnula), sp. Clavatula concinnata, Wood, p. 61, tab. Tii., fig. 11, aff. Tel. 0. nebula, fig. 10. One specimen is 19f mm. long, 8 mm. in diameter; spirae, 11 mm. long. 23. Pleurotoma (Bela) rufa, Mtg. Wood. 13J mm. long, 5J mm. in diameter; spirse, 7 mm. long. 24. Pleurotoma (Ischnula) Treveylliana, Leach. Circ. 11 mm. long; 5 mm. in diameter; anfr. ult., 5 mm. long. 25. Admete viridula, Fabr. One specimen, 10 nim. long. 26. Voluta, sp. Fragmentum spiraa. Anfr. tres primi solum adsunt: anfr. 2 primi laevigati, mamillam formantes; anfr. tertium undatim plicato-costatus. Sutura profunda. Diam. 3 mm. Cancellaria coronata, Wood, tab. vii., fig. 18, gives an idea of it. 27. Trochus amphibola, nov. sp. Testa subperforata conica obtuse-angulata. Anfr. convexiusculi, quadrilirati, iaterstitia lirarum lirulis 2-3 intercalantibus. Labio subreflexo incrassato liris 2-3 obsoletis. Periomphalum declivi angusto. Striae incrementi regularibus membranaceis. Axis, 8 mm.; long, 13 mm.; diameter maj., 12 mm.; min., 10 mm. {Oibhula) very like Margarita cinerea, Couth., but decidedly a Trochus. 28. Trochus (Gibbula). Testa convexo conica, imperforata, carina subprominula acutiuscula. Anfr. declivi planiusculi supra carinam liris 5 bipartitis; basis conferte lirulata interstitiis lirarum carinam versus lirula inter- calante. Striaa incrementi confertse, obliquas, regulares, fili- formes. Axis, 5 mm.; long, 8 mm. diameter maj. 9 mm.; min. 7 mm.; alt anfr. penult, 2\ mm. Allied to Tr. divari- catus, L. One specimen. •29 Patella (Patina) pellucida, L. ? Patella lasvis, Winkler, I.e. p. 211. The surface is, according to Dr. Winkler, smooth, the concentric lines of growth are scarcely to be seen by the lens. Length 9J mm., and 6 mm. broad. 398 Dr. 0. A. L. Mbrch—On the Crag of Iceland.

30. Teredo, sp., tube about 9 mm. in diameter. In a fossil piece of wood. Paykull indicates exactly the layer in which it is found, p. 42. d. 31. Solen siliqua, L. ? In the Spenglerian collection is found a fragment 27 mm. long, and 14 nun. high. 32. Solen- ensis, L. minor, Nyst, I.e., tab. 1, fig. 4. In the same collection a fragment 18 mm. long, 7J mm. high. . 33. Gyrtodaria siliqua, Spgl. Glycimeris angusta, Nyst, p. 55, tab. 11, fig. 1«. (Winkler). Well preserved, often with the ligament. °34. Cyrtodaria Heerii, Winkler, l.c. p. 208. According to a sketch by Dr. Winkler, this species is established upon a rather incomplete specimen. It is 45 mm. long, and 19 mm. high, under the umbo only 13 mm. It looks to me very like Cyrtodaria angusta, Nyst *35. Saxicava (Panomya) Norvegica, Spgl. Panopiea Norvegica, Spgl. Winkler, l.c. p. 208. 36. Corbtdomya complanata, Sowb. Corbula complanata, Sowb., M.C., p. 86, tab. 362, fig. 7, vix 8. Corbviomya complanata, Nyst, Coq. Foss., p. 59, tab. 2, fig. 2 (Winkl.). Corbula complanata, Bronn. Leth. T., 11, p. 69, tab. 37, fig. 8. Corbulomya complanata, Mbrch, Payk. Several specimens exceedingly thick in the shell, 23f mm. long, 13 mm. alt. 37. Corbulomya Winkhri, Morch. Corbulomya complanata, Winkler, p. 206, non Sowb. Corbulomya, sp. Morch, Payk. Testa tenuis postioe angustata juxta umbones ochracea. Long. 29 mm., alt. 15 mm. 38. Corbulomya, sp. ? var. Abbreviata preecedentis f 39. Mya arenaria, L. Mya arenaria, L., Winkler, p. 205, Morch, Payk. Rather common, Winkler, Paykull. The largest is 72 mm. in length, 40 mm. high. 40. Mya truncata, L. Paykull. One specimen 70 mm. long, 48 mm. high. 41. Mactra (Spisula) procrassa, S. Wood. Mactrce solidce, aff., Morch, Payk. 42 mm. long, 35 mm. alt. Cyprina Islandica, var. without lunula or area. ' Winkler, p. 201, belongs perhaps to this. 42. Mactra (Spisula) areuata, Sowb., 1817, tab. 168, fig. 1. Long. 55 mm.; alt. 43 mm. 43. Mactra (Trigonella), sp. Mactra stultorum, L., S. Wood? Morch, Payk. This species closely resembles Cardium Grcenlandicum, Chem.; it is however easily distinguished by the want of the impressed lines outside for the reception of the ligament. 44. Tellina (Macoma) obliqua, Sowb., M.C., tab. 161, fig.1 . Tellina obliqua, Nyst, p. 107, tab. 15, fig.2 . Tellina ovata, Sowb., Winkler, p. 203, Morch, Payk. Dr. 0. A. L. March—On the Crag of Iceland. 399 I give here the measure of some individuals— Long. 36 mm.; alt. 33 mm. » 28 „ „ 23 „ „ 33 „ „ 28 „ Wood, tab. 7, fig. 1. 45. Tellina (Macoma) calcarea, Chem. Tapes virginea, Forbes, Winkler, p. 203, ex figura. Tellina sabulosa, Spgl., Morch, Paykull. Bather common; 28 mm. long, 19 mm. alt. 46. Tellina (Macoma ?) prcBtenuis, Leathes. Tellina prastenuis, "Wood. p. 238, tab. 21, fig. 2. Tellina, sp. Morch, Paykull. Husavig, Spgl., Paykull. 47. Cyprina Islandica, L. Cyprina Islandica, L., Morch, Paykull. The large form is rather scarce. I give here the measures of three individuals. Long. circ. 98 mm.; alt. 85; crassities testae, 4J mm. )9 70 » )> 69 it 4 t> 66? JJ 65 J) t9 3 48. Cyprina,yp spp . Cyprina Islandica, Nyst, p. 145, tab. iz., fig. 1. „ „ " Wood, p. 96, tab. 18, fig. 2. „ • „ Winkler, p. 200. Cyprina Gaimardi, Robert, Morch, Paykull. Cyprina Islandica, Deshayes. In immense banks. The valves are always united and closed, often with the ligament preserved, and with crystals of calcspar. I am very much inclined to consider it a distinct species. A similar dwarf form is found in .Odensefjord, FyoniaJ and, according to Winkler, on the coast of Mecklenburg. Long. 73 mm., alt. 60 mm. •49. Cyprina Gaimardi, Robert. Cyprina Gaimardi, Robert, I.e. p. 285, fig. 51. Probably the same as the following. •50. Cyprina rustica, Sowb. Cyprina lumida, Nyst, p. 148, tab. 10, fig. la-c. Cyprina rustica, Wood, l.c. p. 197, tab. 18 fig. la. The right valve partly preserved. The length is about 45 mm. and the breadth nearly the same ; diameter, 40 mm.; the thick- ness of the shell 4-5 mm. Cyprina Lajonkairii, Goldf., p. 237, tab. 148, fig. 9, quoted by Dr. Winkler; seems to me not to belong to this species. •51. Astarte crebricosta, Forbes. Astarte Hjaltalinii, Winkler, l.c. p. 201. According to Dr. Winkler's drawing not sufficiently distinct a ap. 52. Astarte compressa, L. Astarte elliptica, Brown. A fragment seems to me to belong to this shell. 53. Cardium echinatum, L. Cardium echinatum, Winkler, p. 202, Morch, Payk. Long, testae circ. 55 mm.; costas fere, 3 mm. latse. Dr. Paykull's specimen, with a part only of the shell preserved, indicates a very thick-shelled variety. 400 Horace B. Woodward—On the Metamorphism of Strata. °54. Cardium, sp. A small distinctly ribbed form, not determinable. Winkler, p. 203. 55 Cardium (Serripes) Grcenlandicum, Chem., var. Cardium Grcenlandicum, Wood, tab. 3, fig. la, "Winkler, p. 202. Serripes Grmnlandicus, Chem., March, Payk. Bather common, long. 42 mm.; alt. 35 mm. circ. Spm. jun. „ „ 9 „ ,,8 „ This variety looks most like to the variety from Spitzbergen, called C. Fabricii by Deshayes. Old specimens are rather difficult to distinguish from Mactra without the hinge. The Mactra is, however, easily recognized by the want of the impressed lines for the reception of the ex- ternal ligament of Cardium. 56 Modiolaria nigra, Gray. The nucleus of a rather large specimen. 57. Mytilus edulis, L. A few young specimens, the largest 32 mm., from Paykull. 58. Mytilus hesperianus, Lam., Wood. Mytilus densatus, "Wood, Cat. Tungubakkar paa TjSrnees. The largest specimen is 80 mm. long and 35 mm. high. 59. Lepralia auriculata, Hen., Smitt. 60. Balanus suleatus, Brug. 61. Balanus ovularis, Lam. ?

IV.—NOTES ON METAMORPHISM OP STRATA IN THE MENDIP HILLS. By HORACE B. WOODWARD, F.G.S., of the Geological Surrey of England. A LTHOUGH the Mendip Hills have received a large share of XX attention from geologists since the beginning of the present century, and particularly from Buckland and Conybeare, Weaver, De la Beche, Ramsay, and Moore, there are still many points of great interest that require to be worked out. The object of the present communication1 is to re-direct attention to some instances of silicification which are to be met with in certain formations on the Mendip Hills, and to offer some theoretical re- marks on the origin of this metamorphism. General Description.—On Harptree and Egar Hills, in the neigh- bourhood of Chewton Mendip, and also near Emborrow, reposing on the Dolomitic Conglomerate, the Mountain Limestone, and the Old Eed Sandstone, there (Tccurs a peculiar siliceous deposit. In the upper part it is a compact chert containing shells, lower down come sandy beds; sometimes the chert appears conglomeratic, or rather brecciated, for the fragments contained in it are angular. The entire deposit must attain in places a thickness of 30 feet, but in the 1 I should mention that my observations were made in 1868. and 1869 when engaged with my colleagues, Messrs. W. A. E. TTssher,and J. H. Blake, in re- surveying the Mendip Hills, under the' superintendence of Mr. H. W. Bristow, F.K.S.