CLEMENTIA. 433 



Species of Cyclina. 



Chinensis, Chem. orientalis, Sow. 



flavida, Desk. 



Genus CLEMENTIA, Gray. 



Mantle-margins simple ; siphons long, cylindrical, united; 

 foot quadrate. 



Shell transversely ovate, sub-trigonal, equivalve, inequi- 

 lateral, white, thin. Hinge with a single, anterior, erect 

 tooth, and two oblique, laminated, posterior teeth in the 

 left valve; and two anterior, erect teeth, and a posterior, 

 bifid, laminated tooth in the right valve. Muscular im- 

 pressions two, wide apart, sub-circular; pallial impression 

 widely and deeply sinuated posteriorly; sinus sub -triangular, 

 ascending perpendicularly nearly as far as the beaks. 



Ex. 0. papyracea, Gray, pi. 109, fig. 1, 1, a. 



In this genus the foot of the animal is large and cres- 

 centic, as in Dosinia, and the siphons are elongated and 

 united. The shell is transversely oblong, very thin, and 

 closed ; the surface of the valves is concentrically plicate ; 

 the hinge is composed of compressed teeth, with a cavity 

 in the margin before and behind them ; and the ligament 

 of the hinge is semi-internal. There are six species of 

 dementia known, from Australia and the Philippines. 



Species of Clementia. 



Essingtoniensis, Desk. papyracea, Gray. 



"gracillima, Cpr. similis, Sow. 



granulifera, Sow. vitrea, Chem. 



