Pelecypoda 



27 



Acanthochites^ pyginaens Pilsbry PI. 1, fig. 3 



Length, 10-20; breadth, 5-10 mm. Color pale or deep olive or 

 gray-green; less oval and a little more slender than Chaetopleura 

 apiculata. Dorsal areas well marked, rather flat and moderately 

 keeled. The sides are flat and sloping and quite evenly covered with 

 small papillae. The girdle partly covers the valves and bears nine 

 small tufts of silvery bristles, evenly spaced, on each side, and a 

 sparse beard of bristle on each end. 



This chiton is usually found in shallow water, adhering to dead 

 shells, or crawling in sand near shore line, an unusual habit for a 

 member of this group. 



umbo . 

 lunulor area-, 

 cardinal teeth- 



anterior 

 adductor scar 



dorsal border 



ligamental area 



^- posterior lateral teeth 



posterior 

 adductor scar 



anterior - ■ 

 border 



pallial line ■ 



_ posterior 



border 

 - pallial sinus 



'-- rpvf'-nl herder 

 Fig. 1. Diagram showing the characteristic features of a pelecypod. 



Class PELECYPODA 

 The class Pelecypoda (Gr., pelekys, axe; podos, foot) is in- 

 ferior to the Gasteropoda in numbers of genera and species, but in 

 numbers of individuals it surpasses all other divisions of the Mol- 

 lusca. Along parts of the North Atlantic Coast where Mya arenaria 

 finds congenial circumstances, the littoral area may be almost paved 

 with successive generations of this bivalve mollusk. On the Gulf 



^ Gr., akantho, thorn; Lat., pygmaeus, pygmy. 



