- 170 - 



toat-d-fait i 1 'extr^p/.lt§ aiitdrieure (posterior) du ligament, le 

 mani^re que le lii^ament Ost enti^rement loas de 1 'intervalle qui 

 les s^TDare." A parently it is not "iiovm v/hether such forms actn- 

 all^" belong to the group w'niel- usua^^.lj? receives the nane oennaoea . 

 members of 7/hich do not have the above hinge and ligament charac- 

 ters; and besides have a more angular posterior narf?in, b^it the 

 same sculpture. Oonrad reported one of these from the Duplin of 

 I^orth Carolina, although it has not appeared in siibsequent collect- 

 ions. Because of this uucertaintj' it is do'^btful' whether all of 

 the above citations belong in the synon^raj?. 



G, jamaigensis is more inflated, more angularly produced and 

 keeled nosteriorl^", •.vith less prominent concentric sculuture, a 

 different cardinal area and hinge. 



Occurrence. - lower Miocene : Bowden be^s, Bowden, Jamaica. 

 Miocene.- Duplin formation, ITorth Jaro" ' fJonra'^-, 18S5, etc.). 

 Pliocene.- Dominica, llest Indes (Dall, 1808); Oaloosahatchie 

 marl, Florida ( Jail , 1890). I'ecent.- Forth Carolina to the ■"est 

 Indes and east to Bermuda. 



