378 mactmnjE. 



Genus IIARVELLA, Gray. 



Shell thin, cordate, the hinder slope narrow, keeled. 

 Hinge with the cardinal teeth small; lateral teeth very 

 small, placed close to the cardinal ; hinge-margin double ; 

 ligament marginal, triangular, separated from the cartilage- 

 pit by a shelly ridge. Pallial sinus rounded. 



Ex. H. elegans, Soioerby, pi. 99, fig. 4, 4, a. 



The only representative, at present known, of Harvella 

 is from Florida; the shell is white, very thin, and plicated. 



Genus SPISULA, Gray. 



Shell trigonal, the hinder slope more or less keeled. 

 Hinge with the cardinal teeth moderate ; lateral teeth elon- 

 gate, cross ribbed ; ligament triangular, sub-marginal, near 

 the cartilage-pit, not separated from it by any shelly plate. 

 Pallial sinus small, rounded. 



Syn. Hemimactra, Swainson. 



Ex. S. truncata, Montagu, pi. 100, fig. 1. Shell, S. 

 solida, Linnaeus, fig. 1, a, 1, b. 



Species of Spisula are found in the British seas, the 

 Mediterranean, on the coasts of North and South America, 

 and in Australia. 



Species of Spisula. 



aspersa, Sow. solida, Linn. 



corbuloides, Desk. solidissima, Chem. 



Dysoni, Desk. sublanceolata, Desk. 



elliptica, Brown. subtruncata, Da Costa. 



Mariae, A. Adams. tellinoides, Desk. 



rostrata, Spengl. triangula, Benieri. 



rufescens, Lam. truncata, Mont. 

 Sayi, Gray. 



