352 PROCEEDINGS OF THE NATIONAL ^WSEUM. vol. xxvi. 



This is Chione Gray, 1838, not Megerle, 1811, or Gray, 1851; Dione 

 Gray, 1851, not of Hiibner, Lejndojjtera, 1816; and Oallista Morch, 

 1853, not of Leach, 1852. 



Genus AMIANTIS Carpenter, 1863. 



Type, Cytherea callosa Conrad. 



Shell ovate, concentrically waved, with vernicose periostracum; 

 lunule and a linear escutcheon, defined; inner margins smooth: pallial 

 sinus ample, acute in front, free below, slightly ascending; anterior 

 cardinal very thin; anterior laterals large and strong. 



Section Amiantis s. s. 



Shell with two obscure radial ribs internally, near the middle of the 

 disk; posterior cardinals elongated, strong, the right one bifid, the 

 other teeth entire; the posterior left cardinal and the edge of the right 

 nymph rugose; the posterior right dorsal margin beyond the hinge 

 plate grooved to receive the edge of the opposite valve. Californian. 



This is called Amyanti.s by Stoliczka, 1871. 



Section EucalHsta Dall. 1902. Type, Ch/therea jnirjmixita Lamarck. 



Shell with the posterior cardinals short; the opposite faces of the 

 nymphs with interlocking rugosities; the teeth smooth; interior with- 

 out radial ridges. 



Lamarck himself called attention to the remarkable corrugated areas 

 of this shell which recall those of V..i)iercenarla. It is a Brazilian 

 species which has been confounded with one from west America. 



Genus MERETRIX LaiTiarck, 1799. 



Type, Venus meretTi'X., Linnasus. 



Shell trigonal, plump, thin, nearl}^ equilateral, smooth with a verni- 

 cose periostracum, a peculiar olivaceous tone of coloration; lunule 

 and escutcheon not circumscribed or distinctly defined: three cardi- 

 nals in each valve and well-defined anterior laterals; the middle left 

 and two anterior right cardinals entire, smooth, the others grooved or 

 bifid: right nymph and posterior left cardinal corrugated; anterior 

 left and posterior right dorsal margins beyond the hinge plate sharply 

 grooved to receive the edge of the opposite valve; internal margins 

 smooth; the pallial line with a shallow arcuate flexuosity, but no 

 angular sinus; ligament hardly depressed. 



Distribution chiefly in the China seas, Japan, and the Indo-Pacific 

 region. 



This group is CytJterea (Lamarck) and Citherea Roissy, 1805, and 

 Lamarck, 1806; CytJiersea Defrance, 1818; JSfympha Morch, 1853, not 

 Fitzinger, 1826; and Meretrlx^ ex parte^ Deshayes, 1853. 



