DIAGRAM OF THE HIGHER DIVISIONS REPRESENTED 
IN THIS CATALOGUE. 
( FAMILIEs. 
Strepomatide, 
{ Unionide, 
Corbiculidz. 
: f Philomycenidz, 
s Sus-ORvER. Limacide, 
Nn Helicide, 
5 | GEOPHILA, Succinide, 
is Cuass. Ono | INOPERCULATA. Pupadz. 
i) 1 LIMNOPHILA, f Auriculide, 
& J GASTEROPODA. PULMONIFERA. | INOPERCULATA. Limnaeide. 
| Viviparide, 
. LIMNOPHILA, | Vane ee 
ce} L OPERCULATA. Amnicolide, 
a 
A 
| 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, 
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