CONCHIFEKA OR BIVALVES. 131 



and in the other two corresponding grooves. 

 The lower valve has a longitudinal hole near 



the hinge, and the opening is entirely filled up 

 by the ossification of the tendon passing 

 through it. Besides the muscular impression 

 in the upper valve, there is a mark which 

 shows the attachment of the other extremity of 

 the tendon of adhesion. 



Mr. Cuming found one species of this sin- 

 gular shell attached to dead bivalve shells and 

 coral, at the depth of eleven fathoms in the 

 Gulf of Dulce, in Costa Rica, Central America. 

 It is intermediate, as its name denotes, between 

 Placuna and Anomia: the hinge is like the 

 former, and the opening in the lower valve for 



K 2 



