DONACIM. 403 



margins entire. Hinge with two laminar, diverging teeth 

 in the right valve, and three teeth (the central bifid) in the 

 left valve. Muscular impressions oval, polished; pallial 

 sinus very deep, ascending. 



Syn. Dosinia, Gray, not Scoj). Mysia, Gray, not 

 Leach. Cyclina, Gray, not Desk. Lajonkairia, Desk. 



Ex. L. undata, Pennant, pi. 105, fig. 1. Shell, L. 

 undata, fig. 1, a, 1, b. 



The siphons in this genus resemble those of Tellinidm 

 rather than Vcfieridce, being long, separate as far as their 

 bases, and diverging, with the orifices fringed. The shell is 

 also thin, and with the flexuosity of the Tellens, and there 

 are but two teeth in one valve. Although usually placed in 

 the family Venerida, we have preferred to follow, in this 

 instance, the example of Mr. W. Clark, and to regard 

 Lucinopsis as one of the Tellinida. 



Species of Luchnopsis. 



decussata, Phil. saccata, Gould. 



gibbosa, Gmel. subquadrata, Hartley. 



inflata, Soiv. substriata, Mont. 



Kroyeri, Phil. tenuis, Becluz. 



macilenta, Reeve. undata, Penn. 



Sub-fain. DONACIN^. 



Animal with the siphons short and diverging. 

 Shell more or less wedge-shaped, closed. Hinge with the 

 ligament short, external. 



'O' 



Genus DONAX, Linnseus. 



Shell strong, more or less wedge-shaped, cquivalve ; the 

 hinder side much shorter than the anterior; surface smooth, 



