158 BIVALVES. 



always narrower than the areola. The hinge 

 has either one or two central teeth in each valve, 

 one of them often bifid ; * the lateral teeth are 

 remote, and sometimes wanting in one valve ; 

 the beaks are short, and usually lean towards 

 the ligament, which is external. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



This and the following genus are so very 

 similar, that it is often difficult to discriminate 

 between them. If however a shell have its 

 anterior slope compressed, or any indication of 

 its margin being curved inwards, it may be 

 known immediately as a Tellina. The Tellinae 

 are very beautiful, and are particularly remark- 

 able for the coloured radiations with which they 

 are adorned. They have generally a fine polish, 

 and are sometimes delicately marked with minute 

 striae. They are found buried in the sand or 

 fine gravel of the sea shore; where they are 

 commonly the prey of Buccina, and other car- 

 nivorous mollusks, who pierce the shell, and 

 devour the inhabitant. The mantle of the ani- 

 mal is formed in the front into two siphons ; the 

 foot which it thrusts out of. its shell when de- 

 siring to change its position, is generally flat, 

 but sometimes it is straight and lengthened into 

 a kind of leg. 



* Bifid, cleft in two, from the Latin bis twice, and fid z, I 

 have cleft. 



