152 AMERICAN JOURNAL 



CARDITA, Lam. 



Cardita, Lam., Syst. An. s. Vert. p. 118, 1801. Type 0. 

 calyculata, Lin. 



Subgenus Ceropsis, Dall. 



Shell small, ribbed or sculptured ; with a ^.-shaped cardinal 

 tooth in the right valve ; left valve with a stout anterior and 

 slender posterior cardinal tooth, diverging, and a very slight 

 groove in the posterior margin ; no lateral teeth in either valve, 

 and no groove in the right valve. 



Umbones almost posterior, general form trapezoidal. 



Habits, nestling. Byssiferous ? Animal ? 



This small and very pretty subgenus differs from all the other 

 sections of Cardita in its hinge. Its form suggested affinities 

 with Trapezium, upon a cursory examination ; but, having only 

 two cardinal teeth, it is evident that it forms a section of Cardita. 



Type Ceropsis minima, n. s. 



Trapezium? halioticola, Dall, MSS. 1866. 



Shell minute, trapeziform, white, with a thin brownish epider- 

 mis. Umbones prominent, nearly terminal. Anterior margin 

 rather strongly angulated ; basal margin straight, or a little con- 

 cave ; lower posterior extremity angulated; upper posterior 

 angle rounded off; posterior margin rather oblique. Hinge line 

 smooth, rather broad. Ligament conspicuous, moderately long. 

 A rounded carina passes from the umbo to the lower posterior 

 angle, above which are from two to five radiating ribs. General 

 scufpture of sharp elevated lines of growth, which become 

 vaulted scales on the ribs. Margin lightly crenulated. Interior 

 polished ; muscular and pallial impressions indistinct. Lon. -14, 

 lat. -08, alt -075 in. 



Habitat, nestling or burrowing in Haliotis rufescens, at Mon- 

 terey, also dead on beach, Dall ; nestling under stones at low 

 water, Canfield, Stearns and Cooper. 



As my habitat seems to have been exceptional, I have not 

 retained the MSS. name which alluded to it. Some of the spe- 

 cimens since obtained were larger than the above dimensions, 

 and there was one odd valve from the beach among my collec- 

 tions, which is now out of my possession, which measured nearly 

 •25 in. I am inclined to think it byssiferous, though the valves 

 do not gape. 



