5 GASTEROPODA. 
Shell turriculated, thick; aperture circular, continuous, with 
a large expanded border. 
Fossil, 2 species. Saint Cassian beds, Austria. 
HOLOPELLA, McCoy, 1852 
Example, H. gregaria, Sow. (Turritella), Sil. Syst. t. 3, f. 1. 
Etymology, ’olos, entire, and epe, an aperture. 
Shell elongated, slender, of numerous gradually increasing 
whorls, generally crossed By slightly arched strie; mouth cir- 
cular, with the peristome entire; base rounded, with or without 
a minute umbilicus. 
The shells of the species composing this genus differ from 
those of Yurritelia in the continuous peristome and definite 
round margin to the aperture, thus approaching much nearer 
to Scalaria. 
fossil, 12 species. Silurian—Trias. Europe, United States. 
Famity TV.—MELANIADZ.* 
MELANIA.—Tentacles long, with eyes on the exterior side at 
about a third of the length; margin of the mantle festooned. 
Sub-genera, Vibex, Melanatria, Hemsinus, and 
Philopotanvis, Layard, P. sulcata, Reeve, sp. Operculwm sub- 
spiral; nucleus marginal. Shell solid, paludiniform. Distribu- 
tion, d species. Ceylon. Habit of Tanalia. 
PaLubpomus (Type, P. conicus, Gray), as restricted by the 
separation of Philopotamis and Tanalia, is characterised by the 
conceutric structure of the adult operculum resembling that of 
Paludina, and a spiral nucleus situated about the middle of its 
height, and nearest to the left margin. 
Distribution, India, Burmah, Egypt, East Indian Archipelago, 
Mauritius, Ceylon (2 species, reduced from 14). In tanks and 
marshes. 
Sub-genus, Tanalia, Gray. 
Synonym, Ganga, Layard, founded upon certain monstrous 
forms of 7’. aculeata. 
Type, T. aculeata Chemnitz. 
Shell semiglobose, costate, nodulose; mouth very large, ovate; 
operculum unguiculate; nucleus marginal. 
Distribution, 2 species. Inhabiting mountain streams, ad- 
hering to rocks, or crawling over sandy bottoms, Ceylon. 
Fossil, 2 species. Upper Chalk. Gosau 
* See p. 246, &c. 
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