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Show 320 MR. R. J. L. GUPPY OM HELIX COACTILIATA. [Apr. 20, I would refer to Professor Marcou's map showing the extent of the land which probably existed in the Jurassic period *. If the boundary of the Atlantic land there represented be extended a little southward, so as to take in the island of St. Helena, we can form an idea of the total extent of the land which may have existed during the later Secondary and earlier Tertiary periods f. Nevertheless I cannot overlook the grave difficulties of the problem, in face more particularly of the peculiarities of the African fauna. The observations herein contained may therefore be regarded as suggestions which will be of use when the additional knowledge is forthcoming to enable us to decide on the true relations of the facts. The species of land and freshwater mollusca known to be common to Trinidad, the West-Indian Islands, and the American continent are the following :- Stenogyra octona, Chemn. Pupa (Vertigo) eyriesi, Drouet. caracasensis, Reeve. Streptaxis deformis, Fer. plicatella, Guppy. Succinea approximans, Shuttl. Cionella lamellata, Pot. & Mich. Veronicella lavis, Fer. Helix ierensis, Guppy. Physa rivalis, Mat. & Rack. Bulimus oblongus, Miill. Marisa cornu-arietis, Linn. Orthalicus undatus, Brug. Ampullaria urceus, Miill. Bulimulus tenuissimus, Fer. eflusa, Miill. The following five species have been found in Trinidad and in the Antilles, but are not known to occur on the continent:- Bulimus auris-sciuri, Guppy. Tobago. Pupa bicolor, Hutton (Ennea). Grenada, St. Thomas. Cyclotus grenadensis, Shuttl. Grenada. Cyclas incurva, Guppy. Guadeloupe. Planorbis terverianus, Orb. Cuba, &c. Bulimus auris-sciuri is a race or local form of B. glaber, a species extensively distributed on the continent. Pupa bicolor is supposed with some probability to have been introduced from India. Cyclotus grenadensis is intermediate between the characteristic Jamaican forms and C. stramineus of Venezuela. The two freshwater shells are of South-American type, though the species are known from the Antilles and Trinidad only and not yet recorded from the continent. The species found in Trinidad and on the continent, and not known to occur in the Antilles, are the following nine :- Zonites guildingi, Bland. Porto Cabello. Guppya vacans, Guppy. Venezuelan Guiana. Helix coactiliata, Fer. Venezuelan Guiana. bactricola, Guppy. Venezuelan Guiana. Bulimulus vincentinus, Pfeiff. Carupano (Venezuela). Cylindrella trinitaria, Pfeiff. Carupano (Venezuela). * Marcou, Lettrcs sur les Eoches du Jura : Paris, 180(1. t Eespecting the distribution of land in the Tertiary period, see a paper bv Bourguignat, in Ann. Sci. Nat. Zool. 5e ser. vol. v. (1800) p. 313 and plate 11. |