4S Mr. Martin'j Account of fame Specks of 



namely, a cavity or notch under the beak of the larger valve fur- 

 nifhed with two fmall lateral prominencies ; and in the fmaller valve 

 a projection that corresponds with the notch and hollows that re- 

 ceive the prominencies juft mentioned. But of this a better judg- 

 ment may be formed by comparing Tab. 4. fig. 1, the top of the 

 under valve of an Anomia, known in the recent ftate, and alfo found 

 in great quantities foflil, with fig. 2, a correct drawing of the fame 

 part of a petrified fingle valve of the ftraight-hinged kind. In this 

 laft the cavity a (forming when the valves are united a triangular 

 aperture between the beak and hinge), and the pointed procefles 

 b, b, may perhaps anfwer the purpofe of the notch a, and lateral 

 prominencies b, b, fig. 1, though greatly differing in fhape. That 

 this is at leaft probable will appear, if we examine fig. 5, which 

 reprefents the petrifaction, fig. 2, as commonly found, of folidlime- 

 ftone, with the valves joined. Here it is evident a part of the ca- 

 vity, with the procefles * b, b, of fig. 2, are covered by the upper 

 valve, the hinge of which, as in the recent Anomic?, I fuppofe to be 

 indented into the bottom of the notch, and furnifhed on the infide 

 with hollows anfwerable to the prominencies in the other valve. 

 Before however the whole internal ftructure of the foflil ftraieht- 

 hinged Anomia can be properly determined, it will be neceflary to 

 examine a perfect, detached upper valve, which I have never yet 

 been fortunate enough to meet with. 



Of the Perforation, 

 Some authors, in their definition of an Anomia, have contoured 

 the perforation as the leading or elTential character of the genus, 

 and have even confined it to a particular part of the fhell the 



* In a fpccimcn of a Tingle valve which I have lately met with, thefe proceffes are rot 

 ilraight, as in fig. 2. their points being curved inward, towards the hollow of the valve, 

 jo as to refemble hooks. 



beak 



