74 NERITINA. NERITA. 



'^ N. mrginea is common in collections; it 

 is marked with various lines and dots. 



^' N.Jiiiviaiilis h common in our rivers: you 

 may find plenty in river-sand, of red and brown 

 colours, and various sizes. 



" N. zebra and iV. meleagris are also pretty 

 shells. The little Neriiina viridis, from the 

 West Indian streams, is one of the smallest 

 species, of a pale pellucid green. 



" Nerita is a marine genus. The shells are 

 solid and semi-globose ; the left-margin is trun- 

 cated, the right-margin toothed, or crenulated. 

 This genus is never umbilicated. 



" N. poPita is a handsome shell : it is thick, 

 polished, and variously marked ; the base of the 

 aperture is yellowish. 



"iV. peloronta, the bleeding-Nerite, is marked 

 with a crimson spot. 



" N. tessellaia is sulcated, or furrowed, che- 

 quered with black and white. 



'^ Natlca differs from the former genera in 

 these particulars : the shell is umbilicated ; the 

 left-margin oblique, not toothed, callous, the 

 callosity sometimes covering the umbilicus. The 

 species are numerous, and several are common in 

 collections. " N. aurantius and ^V. millepunc- 

 tata are good shells. 



" lanthwa is the last of the snail-like genera. 

 Its beautiful purple colour renders the shell a 



