Fluviatile Mollusca of Trinidad. 47 
readily be distinguished by the coloration and by the band of 
chestnut above the suture in the present species. There are 
some minor differences. 
As the specific name zonata had been previously applied by 
Lesson to a Helicina, | am under the necessity of giving a new 
name to this species. I therefore propose to call it H. nemoralis. 
It is found on the leaves of trees in the forests. 
Helicina barbata, Guppy. 
(Ann. & Mag. Nat. Hist. ser. 3. vol. xiv. p. 247.) 
This shell is so nearly allied to H. Dysoni, Pf., of Honduras 
(and perhaps also to H. foveata, Pf., of the Antilles) that it is 
possible they are no more than varieties of one species. 
Puysa, Draparnaud. 
Physa rivalis, Maton & Rackett. 
The mantle is ornamented with stripes and undulating bands, 
which, during the life of the animal, seem to be on the shell. 
The dental band is broad, and covered with numerous minute 
teeth, which are simple, slender, and slightly curved. They are 
arranged in fifty or sixty divergent curved rows of about 250 or 
300 each. 
The Trinidad shell does not attain so large a size as that of 
Cuba (P. Sowerbiana, D’Orb.) and the Antilles; but, owing to 
the close resemblance in all other respects, I feel unable to sepa- 
rate it as a species. 
Pianorsts, Guettard. 
Planorbis terversanus, D’Orbigny. 
The greatest breadth of the Trinidad examples is about 
0-4 inch. 
The lingual teeth are numerous, tricuspid, with a broad base. 
The central tooth has two strong, prominent, acute cusps, with 
a small intermediate point. The laterals are somewhat tri- 
angular, the outer cusp being strongly developed, the two inner 
ones merely small points. Outside of the fifth row of laterals 
the teeth become much smaller. 
Vacinuus, Férussac. 
Vaginulus Sloanei, Fér. 
The dental band is broad, the teeth numerous, simple, similar; 
the median row small. In its dentition this species resembles 
the Helicide more than Testacellus. 
The eggs are oval-oblong, transparent, gelatinous, about + inch 
long, and united in chains of ten or twelve. 
