Hinges of Britijh Bivalve Shells, 



169 



if we are to judge by comparifon, it more pro- 

 perly belongs to that genus. 

 The hinge of the F. crajfa is very plain and fimple, 

 con filling of a grooved central tooth and two 

 others, which are remote. One valve, however, 

 has hardly the appearance of remote teeth, though 

 the central tooth in both is equally llrong. 



Htidata, Penn. Br, ZooL No, 51. f- $$' /' 51- 



Tab. XVII. Fig. 17, 18. 



The hinge of the F. undata has a fmall central tooth 



~^ ' fitUoted under the beak of the fhcll, which fits into 



a triangular cavity in the oppofite valve. A deep 



fulcus runs from the beak in the direction of the 



cartilage ilope. 



ARCA. 



Glycymerts, Linf2,Sx/i.JN'at.ed.Cmetrr.j:^^X3' P^^nn, Br.Zool.No,^^. 

 t 58 /. 58. Da Coji. Br, Conch, p. 168. /. 11. / 2. 2. 

 L'Ji. Conch, /. 278. f. 82. Chemn, Conch. 7. /. 57, 



/ 564. 



Tab. XVII f. Fig. I, 2. ^-- 



■** The hinge of the ^rca Glycymeris is femicircular, 

 and on each fide fet with a curved row of flrong 

 tranfverfe teeth, generally from five to ten on each 

 ...•^-I'^^V fide." 



This is Da Cofta's defcription, and is fo far jufl; but 



he tells us that the centre of the hinge is quite 



Vol. VI. /^ fmooth, 



