406 DONACINjE. 



crocatus, Gould. saxulum, Reeve. 



cultus, Hanley. scalpellum, Gray. 



gracilis, Hanley. sernistriatus, Poll. 



incertus, Reeve. serra, Chem. 



Lamarckii, Desk. spiculurn, Reeve. 



lunularis, Phil. transversus, Soiv. 



navicula, Hanley. trunculus, Linn. 



nitidus, Desk. variabilis, Say. 



petallinus, Desk. vellicatus, Reeve. 



pulchellus, Hanley. venustus, Poll. 

 punctatostriatus, Hanley. 



Sub-gen. capsella, Gray. 



Shell ovate-oblong, transverse, rounded at both ends, covered 

 with a greenish epidermis ; margin of valves entire. 



acutangulus, Desk. politus, Poli. 



Owenii, Gray. variegatus, Reeve. 



Sub-gen. heterodonax, Morch (Arcopagia, UOrb., not Leach). 



Shell broad, triangularly rounded, smooth. Hinge with 

 lateral teeth in both valves. 



bimaculatus, Linn. ovalis, Desh. 



nuculoides, Reeve. parvus, Dkr. 



obscurus, Reeve. vicinus, C. B. Adams. 

 ovalinus, Desh. 



Genus IPIIIGENIA, Schumacher. 



Shell transverse, sub-equilateral, closed, gibbous, covered 

 with a thin, olivaceous epidermis; inner margin of valves 

 not crenulated. Hinge with two primary teeth in the right 

 valve, and one cardinal and two nearly obsolete lateral teeth 



