A HEAVY SHELL. 



189 



Pachydesma crassatelloides^ Conr., Pak-i-dez^-ma 

 cras-sa-tel-loi'-des, is the big, hard name which applies 

 to the big, hard shell, a small picture of which is 

 shown in Fig. 162. The pair of valves from which 

 the figure was drawn are five and a half inches in 

 length and weigh over a pound. They are very thick 

 and solid, even to their edges, which are smooth and 

 finely rounded. 



Fig. 162. 



The hinge-teeth are very strong, the heavy and 

 bulged ligament is external, and the pallial sinus is 

 small. Externally the shell is smooth, yellowish- 

 white in color, sometimxes marked with purple rays, 

 and it is partly covered with a glossy epidermis. The 

 inside is pure white, with purple muscle scars. 



