MELANOPSIS. TRACHELIPODA. 57 
somewhat turreted; the volutions smooth, rounded, and 
subcarinated ; aperture subrotund, ovate, or oblong, a little 
angulated above, slightly modified on the inner side by the 
gibbosity of the body volution; operculum corneous with 
concentric lines of growth, and provided with a sublateral 
nucleus. 
Paludina Desnayarsii. Plate IV. fig. 2. 
In some species the spire is much depressed. The Paludine are somewhat 
allied in form to the genera Ampullaria, Valvata and Cyclostoma. They 
differ from Ampullaria in having a horny operculum in place of a testaceous 
one, as also in their general form; and they are distinguished from the two 
latter genera by their concentric operculum, whereas theirs is spiral. 
The species of this genus are not numerous, and inhabit lakes and rivers, ia 
almost all tropical and temperate climates. 
In a fossil state they abound in a thin stratum immediately over the upper 
fresh water formation at Headon Hill, and are the chief mollusks in the Pet- 
worth Marble. 
TRIBE VII.— MELANIDES. 
Fluviatile shells, with the margins of the operculum dis- 
united, and the right one acute at the edge ; animal fur- 
nished with two tentacula. 
Genus LX XII. —~ MELANOPSIS. — Ferussac. 
Generic Character. — Shell oblong, fusiform, or conico- 
cylindrical; spire with from four to fifteen volutions, termi- 
nating in a pointed apex; but decollated in some species ; 
body frequently equal to two-thirds of the whole shell ; 
aperture oblong-ovate, pointed at the upper extremity ; 
outer lip somewhat thickened, and slightly inflected, and 
deeply notched above ; columella twisted, solid, callous, and 
separated from the exterior margin at the base, by a deep 
sinus in most species, but devoid of it in some ; callosity 
thickest at its junction with the upper extremity of the 
aperture ; operculum spiral corneous, and not quite fitting 
the aperture. F 
Melanopsis carinata. Plate IV. fig. 15. Found in 
Greensand, Isle of Wight. 
The apex in the shells of this genus is very subject to erosion, seldom being 
met with complete. 
The Melanopsi inhabit lakes and rivers; the species are but few, and are 
confined to the fresh waters of India, Africa, and the south of Europe. 
In speaking of this genus Baron d’ Audebard De Ferussae says, ‘‘ The 
genus Melanopsis is one of the most interesting of the Mollusca, in consequence 
of the important facts proved by its fossil species, in connection with the his- 
tory of the Tertiary formations, It equally merits attention in a Zoological 
