NERITELLA. IQl 



ous. Head witli a broad, short muzzle; tentacles slender 

 and subulate, with the -eyes on stout peduncles at their outer 



Fig. 203. 



Lingual dentition of NeriteUa redivata. 



bases ; no head-lobes or neck-lappets. Foot oblong, triano-u- 

 lar, the sides simple, without filaments, or lateral membrane. 

 Operculum articulated, shelly, subspiral. Shell depressed 

 or oval, not umbilicated ; spire very short, cavity simple from 

 the absorption of the internal portions of the whirls ; aperture 

 semiovate, not pearly within. 



In this tribe of Scutibranchiate mollusks the sides of the 

 foot are without membranaceous fringes and tentacular fila- 

 ments ; the animal is not voluminous, and the foot is small 

 and never envelops the shell ; in their dental system they 

 resemble the Trochidae, as also in their muzzle-shaped head^s 

 and pedunculated eyes. They are littoral animals, inhabiting 

 the stones and rocks along the shore, feeding on the alo-» 

 that abound in that situation. They appear to be more 

 active during the night, resembling in this respect, the Patel- 

 lidse, which are said to enjoy considerable locomotive powers 

 at that time. 



There are several geuera included in this family which are not 

 fluviatile, and therefore not noticed by me. Such are Nerita, 

 Clithon, and Catillus. The genus NeriteUa alone is referred to. 



]VERITEL,L,A, Humphret. 



Operculum testaceous, the outer surface smooth, with two 

 apophyses, the upper shorter, sometimes dilat- 



ViD" 904- 



ed and crested, the lateral in the form of an ^' 



arched rib. Shell globose, oval, turriculated 

 or conical, thin, often depressed, covered with 



Operculum of 



a horny epidermis ; aperture semilunar ; inner Nerudia recUvata. 



