178 



THE ANIMALS AND MAN 



colored shell looks as if enamelled. Some of the coast tribes 

 of Africa once used, and perhaps still use to some extent, 

 cowries as money. The limpets are among the most abun- 

 dant of the seashore molluscs, their low, broadly conical shells 

 being plentifully scattered over the rocks between tide-lines. 

 The "oyster-drills" are Gastropods with odd spiny shells 



Fig. 88. The giant squid, Ommatostrephes californica. (From speci- 

 men with body, exclusive of tentacles, four feet long, thrown by waves 

 on the shore of the Bay of Monterey, Calif.) 



which do much harm in oyster-beds by settling down on the 

 oysters, boring holes through the shells and eating the soft 

 parts within. The helmet-shells, from which shell cameos 

 are cut, are composed of layers of shell material of different 

 colors. Among the specially beautiful shells are the cone- 

 shells, the olive-shells, the ivory-shells, etc. 



There are two principle groups of Cephalopods, namely 

 the Decapods and the Octopods. The decapods, as their 

 name indicates, have ten feet or arms surrounding the 

 mouth, and the body is usually elongate and containing a 

 homy "pen" or calcareous "bone." This group includes 

 the cuttle-fishes or sepias, from which is obtained sepia ink 

 and the cuttle-fish bone used to feed canary birds. The ink 

 is a secretion which the cuttle-fish discharges when attacked, 



