114 CONCHOLOGY. 



A. eflOusa. A. Guinica. 



A. virens. A. carinata. 



A. avellana. A. intorta. 



A. fragilis. A. conica, 



A. Pealiana.* 



FAMILY XI. 



Neritacea. Four genera. 



1. Genus A''eritina. PI. 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 pectiniform branchia. 



Shell. This genus was formerly classed with the Nerita, 

 which in form it much resembles, but from the circumstance of 

 the latter inhabiting the sea, and Neritinse 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. JVeritina semiconica. 



N. puUigera. N. strigilata. 



N. dubia. N. meleagris. 



N. zebra. N. virginea. 



N. zigzag. N. fluviatilis. 



N. gagates. N. viridis. 



N. lugubris. N. Bsetica. 



N. lineolata. N. caieosa. 



N. fasciata. N. caffra. 



