﻿CRIS'J'ARIA 



229 



ately full, their sculpture not observed ; surface with irregular 

 growth lines, which become somewhat sulcate around the edge 

 of the shell; epidermis, dark brown or blackish; hinge line 

 regularly curved, with epidermal matter folded in throughout; 

 pseudocardinals wanting; in each valve there is a short, im- 

 perfect lateral ; beak cavities shallow, with two or more deep 

 scars; nacre dull, white, somewhat thickened in front, some- 

 times showing the posterior dorsal plications, which are more 

 distinct on the outside of the shell; muscle scars shallow. I 

 cannot say that these shells are dimorphic, but certain speci- 

 mens, which may be males, have a straight posterior ridge, 

 which end's below the median line; in others it is upcurved 

 behind and ends above the median line and these may be 

 females. 



Length 210, height 115, diam. y^i n™- This is an ordinary 

 sized shell; a larger one measures: length 240, height 120, 

 diam. 70 mm. 



Japan. It seems to be abundant in Lake Biwse. 

 Anodon herculeus Sowerby, Conch. Icon., XVII, 1867, pi. in, 



fig- 7- 

 Anodonta (Dipsas) spatiosa Clessin, Conch. Cab. Anodonta, 



1875, P- 173- Pl- Lvii, fig. 2. 

 Cristaria spatiosa von Ihering, Abh. Senck. Nat. Ges.^ XVIII, 



1893. P- 145- — :SiMPSON, Syn., 1900, p. 584. 

 Barbala spatiosa P.^^tdl, Conch. Sam., Ill, 1890, p. 175. 

 Dipsas plicata var. japonica Kobelt, Abh. Senck. Nat. Ges., 



XT, 1879, p. 429, pi. xLVii. 



A very large species, which has quite commonly been taken 

 for C. plicata. It is solider and much more elliptical in outline 

 than that species. 



Subgenus Pletholophus Simpson, 1900. 



Plctliolophus Simpson, Syn., 1900, p. 585. 



Shell short-elliptical, lenticular, but little thickened in front, 

 with compressed beaks, which are sculptiu^ed with low, wide, 

 concentric ridges, scarcely winged in front or behind, pointed 



