GASTEROPODS 357 



area under the apex. The animal has a powerful foot, by means of 

 which it is enabled to cling 1 to a rock with great strength. In order to 

 dislodge it, it is necessary to approach carefully, and, taking the crea- 

 ture unawares, quickly slip a broad knife-blade under the foot, otherwise 

 it is quite impossible to tear it from its resting-place. A. testudinalis lives 

 entirely between tides, and ranges from the northernmost 

 waters to New York. It feeds upon algge and is a very 

 sluggish animal. It has been said to leave its resting-place 

 and wander about in search of food, returning to its original 

 and usual spot when the tide begins to ebb. (Page 343.) 



A. testudinalis, variety alveus. This variety is smaller, 

 more fragile, and oblong. It lives upon eel-grass, its oblong 

 shell being adapted to the narrow leaves of the grass. The 

 coloration is brighter reddish-brown spots on a white sur- 

 face. It is exceedingly common on the New England 



COast. alveus. 



A. tnitra. On the Pacific coast there are a number of 

 acmaeas. A. mitra is often found dead upon the beaches. It is conical 

 in form and pure creamy- white in color. It looks very much like a 

 clown's pointed cap. 



A. patina. This is also very abundant in California. Outside it is 

 dark in color and is often incrusted with mineral deposits. Within there 

 is a dark ring around the edge, then a zone of bluish- white, and a patch of 

 brown just beneath the apex. 



GENUS Lottia 



L,. gigantea. This is the largest of the California limpets. Specimens 

 three inches long have been found. The outer surface of the shell is 

 rough and brownish in color. The apex is near one end. Within it is 

 almost black, shining, lustrous, with a horseshoe-shaped muscle-scar 

 under the apex. The color is bluish and brown. (Plate L XV.) 



FAMILY FISSUBELLIDJE 



This is an extensive family, including several genera and a 

 number of species, commonly known as keyhole-limpets. In 

 the general form of the shell they closely resemble the true 

 limpets, the Acmceidce, except that they have a hole, or rather a 

 slit, in the shell just back of the apex. Often this slit is so long 

 that it has entirely removed the apex of the conical shell. 



F. altemata, F. barbadensis. These species occur upon the south- 

 ern shores of the United States, the latter, however, being confined to 



