Fluviatile Mollusca of Trinidad. 43 
which, I am of opinion, ought to be separated therefrom. I think 
that the peculiar animal of B. oblongus may entitle it to generic 
distinction, though it remains to be seen if any of the most 
nearly allied forms have similar animals. Then Bulimus octo- 
noides and B. earacasensis seem also to deserve separate places. 
Pfeiffer, Beck, Albers, Chenu, and many others have adopted 
and devised genera for the reception of similar forms; but, as 
each author appears to have his own peculiar views as to what 
species shall be included in each particular genus, and as in the 
majority of cases I feel myself unable to subscribe to those views, 
it seems to me that the only course left open is the one I have 
adopted. 
Neritina, Lamarck. 
Neritina microstoma, D’Orb. 
The Trinidad examples agree with specimens from Cuba, and 
also with D’Orbigny’s description and figures in the ‘ Moll. 
de Cuba ;? but they do not accord so well with the examples in 
the British Museum. Some of the specimens of N. virginea 
strongly resemble the Trinidad shell. 
Parupestrina, D’Orbigny. 
Paludestrina spiralis, Guppy. 
Bithinia spiralis, Guppy, Ann. & Mag. Nat. Hist. ser. 3. vol. xiv. p. 244. 
Further observation has enabled me to refer this mollusk to 
D’Orbigny’s genus, and to add the following remarks :— 
The operculum is thin and paucispiral, its nucleus subcentral. 
The eyes are on bosses on the outer and hinder sides of the 
tentacles. The animal strongly resembles that of Skenea. It is 
viviparous, and about November it contains eggs and young in 
every stage of development. The young shell is depressed and 
umbilicate, and resembles Skenea planorbis. Before birth the 
young mollusk is already furnished with an operculum. 
Lingual teeth 3.1.3: central with a triangular, reflexed, 
serrate edge ; first lateral small, serrate; second transverse, ser- 
rate on the reflexed edge; third slender, claw-shaped, serrate. 
This dentition, though not altogether unlike that of some of the 
Melaniadz, presents considerable resemblance to that of certain 
of the Calyptraeadee. 
AMPULLARIA, Lamarck. 
Ampullaria urceus, Miller. (A. rugosa, Lam.) 
The animal is black, and the left siphon, when fully protruded, 
is longer than the shell. The right siphon is short. The head 
is produced into two lobes, which are extended into acute tenta- 
cular processes. ‘The eyes are well developed, and hard, like 
