MULINIA. 379 



Sub-gen. oxtperas, Morch. 



Shell triangular, wedge-shaped, solid, transversely plicate. 



Eequilatera, Desk. triangularis, Lam. 



transversa, Desk. 



Genus MACTRA, Linnreus. 



Shell ovate, trigonal, sub-angular at each end. Hinge 

 with the cardinal teeth moderate; lateral teeth distinct; 

 ligament external, in an oblique, triangular groove opening 

 into the upper edge of the cartilage-pit. Pallial sinus 

 angular. 



Syn. Capisterium, Meuschen. Scissodesma, Schizo- 

 desma, Gray. 



Ex. M. Spengleri, Linnaeus, pi. 100, fig. 2, 2, a. 



The most striking peculiarity in the shells of this genus 

 consists in the oblique triangular fissure which commu- 

 nicates with the cartilage-pit. The two species known are 

 from Africa. 



Species of Mactra. 

 nitida, Schro'eter. Spengleri, Linn. 



Genus MULINIA, Gray. 



Shell ovate, trigonal, sub-angular at each end. Hinge 

 with the cardinal teeth strong; lateral teeth short, simple; 

 ligament internal, in the same closed pit as the cartilage. 

 Pallial sinus angulated. 



Syn. Moulinea, Phil. 



Ex. M. edulis, King, pi. 100, fig. 3. Shell, M. edulis, 

 fig. 3, a, 3, b. 



