﻿182 



NERITACEA.— Four Genera. 



Shell semifluviatile or marine, semiglobular or flattened oval, without col- 

 umella, the left margin of the aperture resembling a half partition. 



I. FRESH WATER SHELLS. 



Navicella. Shell elliptical or oblong, convex above, summit straight, 

 depressed to the margin, concave beneath; the left lip flattened, sharp, nar- 

 row, without teeth, transverse. A solid, flat operculum, having an acute and 

 lateral tooth. 



N. elliptica, 



N. lineata, 



N. tessellata, 



N. porcellana. 



Neritina. Shell thin, semiglobular or oval, flattened beneath, not um- 

 bilicated; aperture semicircular, the left margin flattened, sharp; no teeth or 

 crenulations on the surface of the right margin. Operculum furnished with a 

 lateral tooth. 



N. perversa, 



' pulligera, 



' dubia, 



' zebra, 



' zigzag, 



' gagates, 



' lugubris, 



N. 



corona, 



brevi-spina, 



crepidularia, 



auriculata, 



Domingensis, 



fasciata, 



lineolata, 



N. semi-conica, 



' strigilata, 



' meleagris, 



' virginea, 



' fluviatilis, 



' viridis, 



' Boetica, 



N. Oweniana, 



' careosa, 



' Caffra, 



' Smithii, 



' spinosa, 



' Oweni, 



' pulchella. 



II. MARINE SHELLS. 



Nerita. Shell solid, semiglobular, flattened beneath, not umbilicated; 

 aperture entire, semicircular, the left margin flat, septiform, acute, often 

 toothed; teeth or crenulations on the inner surface of the right lip. Oper- 

 culum with a projecting tooth. 



'J. exuvia, 



N. atrata, 



N. Ascensionis, 



N. tassellata, 



' textilis, 



' polita, 



' Malaccensis, 



' signata, 



' undata, 



' albicilla, 



' lineata, 



' ornata, 



' peloronta, 



' chamceleon, 



' scabricosta, 



' australis, 



' chlorostoma, 



' versicolor, 



' plicata, 



' rudis. 



Natica. Shell subglobular, umbilicated; aperture entire, semicircular; 

 left lip oblique, not toothed, callous; the callosity modifying the umbilicus, 



