GASTEROPODS 357 
area under the apex. The animal has a powerful foot, by means of 
which it is enabled to cling 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 fromits resting-place. A. testudinalis lives 
entirely between tides, and ranges from the northernmost 
waters to New York. It feeds upon alge 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 alvews. This variety is smaller, 
more fragile, and oblong. It lives upon cel-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 #00 “suai 
coast. alveus. 
A. mitra. On the Pacific coast there are a number of . 
acmeas. 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 LXV.) 
FAMILY FISSURELLIDE 
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 Acme@ide, 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. 
Genus Fissurella 
F. alternata, F. barbadensis. These species occur upon the south- 
ern shores of the United States, the latter, however, being confined to 
