320 MR. R. J. L. GUPPY ON 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 boun- 
dary 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+. Nevertheless 
I cannot overlook the grave difficulties of the problem, in face more 
particularly of the peculiarities of the African fauna. The observa- 
tions 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 mollusea known to be common 
to Trinidad, the West-Indian Islands, and the American continent 
are the following :— 
Stenogyra octona, Chemn. Pupa (Vertigo) eyriesi, Drouét. 
caracasensis, Reeve. Streptaxis deformis, Fer. 
plicatella, Guppy. Succinea approximans, Shuttl. 
Cionella lamellata, Pot.& Mich. Veronicella levis, Fér. 
Helix ierensis, Guppy- Physa rivalis, Mat. & Rack. 
Bulimus oblongus, Mill. Marisa cornu-arietis, Linn. 
Orthalicus undatus, Brug. Ampullaria urceus, Mill. 
Bulimulus tenuissimus, Fér. 
effusa, Mill. 
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-sciurt 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. Cyelo- 
tus 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, Fér. Venezuelan Guiana. 
bactricola, Guppy. Venezuelan Guiana. 
Bulimulus vincentinus, Pfeiff. Carupano (Venezuela). 
Cylindrella trinitaria, Pfeiff. Carupano (Venezuela). 
* Marcou, Lettres sur les Roches du Jura: Paris, 1860. 
+ Respecting the distribution of land in the Tertiary period, see a paper by 
Bourguignat, in Ann. Sci. Nat. Zool. 5® ser. vol. y. (1866) p. 313 and plate 11. 
