406 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 52. 



smooth appendage of which the distal end is internally flattened and 

 somewhat separated from the appendage of the opposite valve, the 

 ends being rounded. 



CBENELLA ROTUNDATA, new species. 



Shell small, rounded-quadrate, inflated, with a very thin, dehiscent, 

 pale ohve periostracum ; beaks central, inconspicuous, with no crenu- 

 lations beneath them; sculpture of faint incremental lines and obso- 

 lete radial striae near the margin; inner margin very delicately 

 crenulate except near the beaks. Length, 4; breadth, 4; diameter, 

 2 mm. Cat. No. 129305, U.S.N.M. 



Station 2849, off Santa Cruz Island, California, in 155 fathoms, 

 sand. 



DERMATOMYA BUTTONI, new species. 



Shell small, rounded-quadrate, plump, thin, yellowish olive, hardly 

 polished, smooth, with iridescent reflections from under the perios- 

 tracum when fresh; beaks nearly central, not prominent, hinge teeth 

 normal, strong; interior bluish white, margins entire, paUial sinus 

 shallow. Length, 9.8; breadth, 8; diameter, 6 mm. Cat. No. 

 194309, U.S.N.M. 



Station 3670, Monterey Bay, in 581 fathoms. 



DERMATOMYA BERINGIANA, new species. 



Shell large, thin, plump, inequilateral, anterior end shorter, base 

 arcuate, anterior end rounded, posterior dorsal slope first oonvexly 

 slightly arcuate, then obliquely subtruncato to meet the basal curve; 

 beaks prominent, 7 mm. behind the anterior end; surface smooth, 

 except for faint incremental irregularities, iridescent under a pale 

 olive, polished periostracum; beaks slightly prosocoelous, hinge weak, 

 the teeth minute, the ossiculum well developed; interior whitish, the 

 pallial sinus very shallow. Length, 20; height, 14; diameter, 12 mm. 

 Cat. No. 205899, U.S.N.M. 



Bowers Bank, Bering Sea, in 557 fathoms. 



DERMATOMYA LEONINA, new species. 



Shell large for the genus, mactriform, solid, inflated, transverse, 

 with a dull olivaceous periostracum, darker, and concentrically 

 wrinkled on the posterior dorsal area; surface smooth exc-ept for fine 

 incremental lines and microscopic radial striulae often obsolete; 

 beaks high, slightly prosocoelous, nearly central; base moderately 

 arcuate, anterior end rounded, dorsal slopes nearly straight, a shallow 

 radial depression on the posterior dorsal area, posterior end subtrun- 

 oate; hinge weak, ligament deeply inset; hinge teeth almost obso- 

 lete; margins entire, pallial sinus shallow, ulterior feebly iridescent 



