GUPPY— MOLLUSCA OF TRLSTDAD. 
35 
on the angle of the whorls. It is common in many of our 
northern streams. 
Height 4 mill, diameter mill. 
Class CONCHIFERA. 
Acephalous Mollusca with two lateral plates or valves. 
Subclass Asiphonida. 
Pallial line simple : animal without respiratory siphons. 
Order TJnionacea. 
Bivalve shells, pearly within, and having a hard dark 
periostraca. 
Anodon Cuvier 1798. 
Fluviatile Conchifera with oval inequilateral somewhat 
auriculated close shells, an external ligament, a simple 
pallial impression and a hinge without teeth. 
Anodon Leotaudi Guppy. 
Ann. Sf Mag. Mat. Hist. 3 ser. vol. 17, p. 54. 
This is the only fluviatile bivalve known to be found in 
this island. It is of an oval-oblong shape, and it is cover- 
ed with a dark olive-brown epidermis ; the interior is finely 
iridescent. Length 82 mill., height 45 mill., thickness 30 
mill. 
It is found in some of the streams flowing into the Caroni. 
The preceding paper was illustrated by diagrams and 
specimens ; and the Author gave a general sketch of the 
organic world, pointing out the position and characters of 
the Mollusca, of the principal groups of which he gave a 
succinct account. 
