UNIVALVES. NERITA. 133 



its whirls crowned with spines of an unequal length : the 

 latter is an inhabitant of the rivers of Europe and Barbary ; 

 it is usually marked with scaly spots, and is sometimes 

 rugged, streaked, or reticulated. 



The species of the third division are distinguished from 

 those of the preceding by having their lips toothed : the 

 principal are the N. puUigera, N. atrata, N. undulata, 

 N. larva, and N. virginea, the latter of which is an inha- 

 bitant of the rivers of South America and India; like ma- 

 ny other species of the Neritas, it is toothed on the inner 

 lip only. Its varieties are extremely beautiful, and are of- 

 ten called the Guinea-hen or Guinea-fowl Nerites, from 

 the resemblance of its markings to the plumage of the bird 

 so named. 



The varieties of the N. polita are the most beautiful of 

 this genus ; they are smooth polished shells, and are ge- 

 nerally clouded with green, having intermediate maculate 

 bands of pale pink; but the most rare variety has three 

 or four bright crimson bands on a dark mottled ground, 

 running in a parallel direction with the convolutions of 

 the shell. These shells are frequently worn as ornaments 

 by the Indians. 



Some species of this division are strongly ribbed or 

 grooved, as the N. histrio, N. plicata, N. grossa, N. pica, 

 and the N. chamaeleon ; which last is varied by alternate 

 undulated black and white rays. 



The N. turrita, from the Antilly Isles, and the N. acu- 

 leata, from India, are fresh-water species. 



The different species of Neritte are produced in the Afri- 

 can, American, Indian, European, and Red seas; the 

 Southern and Northern oceans, the Mauritius, the Cape 

 of Good Hope, and New Zealand. 



