GUPPY— -LAND 4ND FRESHWATER SHELLS OP TRINIDAD. L9 
the middle of the bach, and reflected over a small horny 
shell, which it often completely covers, but is occasionally 
retracted, so as to expose the central portion : foot large, 
lanceolate, and coming somewhat abruptly to a point 
behind. 
The pulmonary orifice is situated at the middle of the 
right side of the mantle. When fully expanded, the 
length of the largest example found was about 16 mill., 
and its breadth about 6 mill. 
The shell is oval, wider anteriorly, of a pellucid horny 
texture, straw-colored, distinctly concentrically striate, 
with microscopic radiating lines ; the edges are sharp and 
scarcely interrupted by a small notch at the junction of 
the right and left margins ; the spire is small and some- 
what prominent. The shell of the largest specimen was 
9 mill, long and 5 mill broad. 
The species belongs to the section Omalonyx , and is 
closely allied to 0 . unguis Fer. 
When describing Amphibulima pardalina in my paper on 
the shells of Dominica (Ann. & Mag. Nat. Hist., June 
1868), I pointed out the necessity for a separation of the 
genus Amphibulima from Succinea , in which some authors 
had located the species, and of regarding Omalonyx and 
Brachyspira * as sections or subgenera of Amphibulima. My 
views on this head seem to have been anticipated by 
d’Orbigny, who, in his description of Omalonyx gayana, 
refers to Amphibulima pa tula, evidently regarding the two 
0 as congeneric, according to our present views of genera. 
* But some of the species included under tire head of Brachyspira 
in Alber’s Die Heliceen are true_Suocinese, e.g. th$ North American 
effuw and /S'. $all$ana, 
