ENTODESMA. 203 



on the shores of the San Francisco bay, and which 



lives along the whole line of 

 coast. In shape it is oblong, 

 bulged at one end; while at 

 the other it is narrow, thin 

 Fi s- 1 7°- and crooked. The outer 



coat shows many concentric striae, but this is easily 

 rubbed off, revealing the inner layer of the shell, 

 which is nacreous or pearly. Its length is an inch or 

 an inch and a half. 



Our next species is named Entodesma sctxicola, 

 Baird, En-to-dez'-ma sax-ik'-o-la. It is a singular 

 mollusk, living in holes of various shapes and taking 

 whatever form is most convenient. Its shell is oblong, 

 bulged at the hinge end, gaping beneath, and pro- 

 longed at the rear end into a somewhat irregular and 

 elastic tube composed chiefly of epidermis. The whole 

 shell is thin and is covered with a yellow epidermis; 

 internally a little ossicle or plate covers the hinge. 



The variety cylindrica has a thicker shell, is very 

 rough, and is somewhat wedge-shaped. Length about 

 an inch; northern. 



Entodesma inflata, Conr. , in-fla-'-ta, resembles the 

 last, but is smaller, thinner, and more irregular, and 

 is composed largely of epidermis. Narrow in front, 

 wider and thinner behind; southern. 



Mytilimeria Nuttalli, Conr., Myt-il-i-me'-ri-a Nut- 

 tall'-i, is a singular mollusk which may sometimes be 

 found imbedded in a soft substance, probably a kind 

 of sponge. The shell is very thin, white, covered 

 with a brown epidermis. There is an ossicle under 

 the hinge. In shape it resembles an inflated bladder, 

 with the spiral umbones at one end. Its height is 

 about one inch. 



