178 BIVALVES. 



ance of the keel. The form of the shell sug- 

 gested the name of Noah's Ark, and from this 

 fancied resemblance in one species to the ark, the 

 genus owes its designation. 



This shell is affixed to rocks by a very strong 

 tendinous substance, there is an open space in the 

 front of the valves, through which it issues. 



It inhabits the Mediterranean, Indian ocean, 

 "West Indies, and Britain. 



ARCA Undata* 



LETTERED ARK. 



Specific Character. Shell suborbicular, nearly 

 smooth, with faint reticulated j* striae ; margin 

 crenated ; teeth in a curved line ; colour white, 

 variegated with yellowish red spots, in undulated 

 transverse bands. 



Inhabits the West Indies, and shores of Italy. 

 It belongs to the modern genus Pectunculus. 



Genus OSTREA$ Plural, Ostrea. 



OYSTER, SCALLOP, OR PECTEN. 



Generic Character. Shell bivalve, generally 



* Plate IX. figure 5. 



^ Reticulated, having the appearance of net work, from 

 the latin reticulum, a small net. 



J Plate IX. figures 7, 8. 



