FOSSIL GASTROPODS. 



249 



Various shells, such as Marginella, Tnrbinella, etc., are 

 strung in bracelets and armlets by savages. Cyprcea moneta, 

 the cowry, is used for African money, and other shells are 

 worked into various shapes for wampum or aboriginal money. 

 On the other hand, an Olivella is used by the California!! 

 Indians as money. Murex and Purpura afford th-e Tyriau 

 dye. Allied to the latter is the whelk (Buccinum undatum). 

 While a few Gastropods are pelagic, living upon the high 

 seas, such as lanthina and the Nudibranch Glaum s, most 

 of the species are submarine and live in all seas; the hardier, 

 most widely diffused species living between tide-marks, the 

 more delicate forms in deep water, ranging from low-water 



a 



Figs. 20-1-205. The whelk; its tentacles ana proboscis exttiiUecl; , egg-cap- 

 sules; 6, embryo shell. (Natural size.) 



mark to fifty or one hundred fathoms. The abyssal fauna at 

 the depth of from 500 to about 2000 fathoms has a few char- 

 acteristic mollusks. Many live on land and in fresh water. 

 The largest, most highly colored shells live in the tropics, 

 while those found in the temperate zones are less beautiful, 

 and the arctic species are the smallest and dullest in color. 

 The shells of the eastern coast of North America are 

 divided into several assemblages, or faunae, the West Indian 

 or tropical shells, in some cases, reaching as far north as 

 Cape Hatteras ; between this point and Cape Cod a north 

 temperate assemblage occurs, and north of Cape Cod the 

 molluscan fauna is essentially Arctic ; many species being 

 common to the arctic and subarctic seas of the circumpolar 

 regions. 



