CONCHOLOGY. 



liar form of their shells, for collectively almost every genera of the 

 spiral univalves fall under this very general denomination, as well as 

 many of those shells which are simply conic, as in the Linnsean 

 classification they do under that of Limax. Cuvier mentions as a 

 character of this tribe that their breathing apertures, with the excep- 

 tion of a family he calls Cyclostomes, are composed of a number of 

 foliations ranged parallel to each other like the teeth of a comb. 

 They have two feelers, and two eyes usually situated on a pedicle. 

 The greatest difference between these animals consist in the presence 

 or absence of the canal formed by a prolongation of the edge of the 

 pulmonary cavity of the left side, a respiratory organ communicating 

 with others by means of which the animal breathes without quitting 

 its retreat in the water. 



According to Lamarck the animal of Nerita has the foot large 

 and short, with two pointed feelers, and the eyes raised upon a 

 papilla at the exterior base of each. 



Bosc is less diffuse than either. The animal of the Nerites, he 

 observes, have the head flat and lunate, a little sloping to the two 

 extremities : from the base of the head on each side issues two conic 

 slender horns, one of which is twice the length of the other. The 

 eyes are two little black points placed upon a trihedral tubercule at 

 the exterior base of the horns, the mouth placed underneath the head 

 and formed with a lip, thick and wrinkled. The foot almost round. 

 Hat beneath, convex above, and rather shorter than the shell. The 

 mantle or fleshy prolongation entirely covers the interior of the shell 

 and is slightly crenulated at the margin. 



Denys de Montfort speaking of the species Nerita Peloronata^ a 

 shell abounding on the shores of the Antilles, observes that there are 



