MACOMA. 



I 9 I 



Heterodonax bimaculatus, D'Orb., Het-e-ro-do'-nax 

 bi-mak-u-la'-tus. Shell oval, rather flat, marked 

 with fine concentric lines. Ligament external, hinge- 

 teeth small and central, pallial sinus half the length 

 of the shell. Color white or purple, length less than 

 an inch, southern. 



The rather large, thin, glossy shell shown in Fig. 

 163 bears the name Macoma secta, Conr., Ma-ko'-ma 



Fig. 163. 



sek'-ta. The general form of the shell is oval, but 

 the posterior end is suddenly contracted. The pallial 

 sinus, as in all of the group, is large, indicating that 

 the animal is a good digger, and the ligament is 

 strong, broad and external. A thin epidermis is fre- 

 quently found round the edges. The length of this 

 shell is two or three inches, and it is found from 

 Monterey southward. 



