114 CONCHOLOGY. 
A. effusa. A. Guinica. 
A. virens. A. carinata. 
A. avellana. A. intorta. 
A. fragilis. A. conica. 
A. Pealiana,* 
FAMILY XI. 
Neriracea. Four genera. 
1. Genus Weritina. Pl. X. 
Animal. Globular; foot circular, thick, without a furrow ante- 
riorly, or a lobe for the operculum posteriorly, with a bipartite 
columellar muscle; conical tentacula; eyes subpedunculate at 
their external side; mouth without labial tooth, but with a den- 
ticulated tongue prolonged into the visceral cavity; a single 
large pectinitorm branchia. 
Shell. ‘Vhis genus was formerly classed with the Nerita, 
which in form it much resembles, but from the circumstance of 
the latter inhabiting the sea, and Neritine fresh water, it now 
forms a separate genus. Thin, smooth, or finely striated, in all the 
species known, the right side of the aperture does not possess any 
crenulations or teeth; the operculum is provided with a lateral 
tooth on one side. Some species are armed with spines; aper- 
ture semicircular ; left margin smooth and sharp ; spire imperfect, 
generally dissolved by the animal. Inhabits the fresh water 
rivers of Europe. ‘Twenty-seven species. 
Neritina perversa. Neritina semiconica. 
N. pulligera. N. strigilata. 
N. dubia. N. meleagris. 
N. zebra. . N. virginea. 
N. zigzag. N. fluviatilis. 
N. gagates. N. viridis. 
N. lugubris. N. Betica. 
N. lineolata. N. careosa. 
N. fasciata. N. caffra. 
