OALLj NEW SPECIES OF SHELLS 1 73 



portionately more inflated; anterior end rounded, posterior slightly 

 attenuated ; hinge-line nearly straight, base arcuate ; sculpture of 

 (on the middle of the disk, 10 or 12) rounded, moderately elevated, 

 radial ridges with wider interspaces near the base, but crowded near 

 the beaks ; the periostracum near the end of the shell exhibits minute 

 radial wrinkles, but the terminal fourths of the valves are destitute 

 of sculpture except faint concentric irregularities. Interior smooth, 

 slightly pearly, with a shallow rounded pallial sinus and faint mus- 

 cular scars ; basal margins crenulated by the sculpture, thin, sharp ; 

 hinge typical, ligament and resilium weak. Lon. of largest valve, 

 48 ; of pair, 44 ; alt., 30 ; diam., 25 mm. 



Station 4807, off Hakodate, in 44 fathoms, and station 4904, in 

 107 fathoms, near Nagasaki, Japan. U. S. Nat. Mus., 110,545 and 

 110,456. 



This is the first recent species, which has been brought to notice 

 since the description of the Antillean P. Candida in 1823, except a 

 minute abvssal form from the North Atlantic. 



