262 MANUAL OF THE MOLLUSCA. 
shelly, with a flexible border; slightly toothed on its straight 
edge. 
Animal like nerita ; lingual teeth ; median, minute; laterals 
3,1 large, sub-triangular 2, 3 minute; uncini about 60, first 
very large, hooked, denticulated ; the rest equal, narrow, hooked; 
denticulated. 
The neritinze are small globular shells, ornamented with a 
ereat variety of black or purple bands and spots, covered with a 
polished horny epidermis. They are mostly confined to the fresh 
waters of warm regions. One species (N. fluviatilis) is found in © 
British rivers, and in the brackish water of the Baltic. Another 
extends its range into the brackish waters of the North American 
rivers; and the West Indian N. viridis and meleagris are found 
in the sea. 
°N. crepidularia has a continuous peristome, and approaches 
navicella in form; itis found in the brackish waters of India. 
N. corona (Madagascar) is ornamented with a series of long 
tubular spines. 
_ Distribution, 111 species. West Indies, Norway, Britain, 
Black Sea, Caspian, India, Philippines, Pacific, West America. 
Fossil, 20 species. Eocene—. Britain, France, &c. 
NAYVICELLA, Lam. 
Etymology, navicella, a small boat. 
Type, N. porcellana. Pl. IX., Fig. 41. 
Shell, oblong, smooth, limpet-like; with a posterior, sub- 
marginal apex; aperture as large as the shell, with a small 
Fig. 113. Navicella. (Wilton.) 
columellar shelf, and elongated lateral muscular scars; oper- 
cultim very small, shelly. 
Distribution, 33 species. India, Mauritius, Moluccas, Aus- 
tralia, Pacific. 
Navicella inhabits fresh waters, adhering to stones and plants. 
Median tooth small; laterals 3, first large, trapeziform, 2, 3, 
minute; uncini numerous, first large, strong, and opaque, the 
rest slender, translucent, with denticulate hooks (Fig. 113). 
