HOOF SHELL. 75 



Hip'-po-nyx an-ti-qua'-tus, the Horse-hoof shell. 

 Fig. 59 gives a side-view of a flat specimen, showing 

 the apex near one side, and part of the 

 interior. The shell is very variable, 

 but in general it is hoof-shaped, with 

 an internal muscular impression shaped 

 Fi s- 59- like a horse-shoe. The lines of growth 



give it a more or less scaly appearance. Sometimes 

 it is nearly flat, but in other specimens it is obliquely 

 conical. The color is white, and the diameter is 

 half an inch. Occasionally live specimens may be 

 found at low tide on the surface of rocks. 



Hipponyx tumens, Cpr., tu'-mens. Smaller and 

 more regular than the last species. Apex recurved ; 

 lower part of the shell sometimes bearded. Radial 

 lines of sculpture run from the apex, and are crossed 

 by concentric lines of growth. 



The Slipper-shells next invite our attention. They 

 are easily recognized by the deck which runs across 

 the back part of the shell, forming a chamber which 

 contains some of the internal organs of the little 

 inhabitant, and which, when the shell is empty, 

 reminds one of the toe of a Chinese slipper. 



The most common species is Crepidttla adunca, 

 Sby., Cre-pid'-u-la ad-un'-ca, Hooked Slipper-shell, 

 shown in Fig. 6o. The apex is strongly 

 recurved, giving the shell a hooked 

 appearance. Its color is brown, but 

 Fig. 6o. the deck is white. Living specimens 



may often be found growing upon rocks or upon 

 other shells. Common length from one-half to three- 

 fourths of an inch ; abundant. 



Larger and more flattened than the last shell, is 



