DIAGRAM OF THE HIGHER DIVISIONS REPRESENTED 

 IN THIS CATALOGUE. 



CLASS. 



ORDER. 



GASTEROPODA. PULMONIFERA. 



ACEPHALA. 



BRANCHIFERA. 



Class GASTEROPODA. 



Animal, head distinct, tentacles four, sometimes two; 

 eyes at the tip, or near the base, of the superior pair ; 

 body more or less enclosed by the mantle; beneath with 

 a dense, elongated, flattened disk (the foot). In the 

 shell-bearing species, the posterior part of the body is 

 enclosed in the shell. The respiratory, and anal orifices, 

 are placed near together on the right side of the neck. 

 Bisexual, but requiring the union of two individuals for 

 reciprocal fecundation. 



Shell, mostly present, and spiral, as in the snails; 

 sometimes only rudimentary, or absent, as in the slugs. 

 When the shell is complete, the mantle covers the upper 

 exterior parts of the animal, and forms a broad, flat ring, 

 by its posterior margin, which closes the aperture of the 

 shell when the animal is extended. 



The animals comprised in this class are more highly 

 organized, and their anatomy is more complex, than 

 other molluscous animals. Besides the organs herein 

 described, which pertain to their family, and generic, 



is 



