NO. 1312. SYNOPSIS OF THE VENERIDM-DALL. 347 



section. The young do not retain any corrugations on the posterior 

 cardinals. 



Section Austrodosinia Da;l, 1902. Type, Gy therm anus Philippi. 

 New Zealand. 



Lunule deeph' impressed, escutcheon impressed and bordered by 

 prominent keels; pallial sinu.s short and angular; anterior lateral and 

 the pit into which it is received, and usually some of the anterior car- 

 dinal teeth sharply corrugated; the middle cardinals bifid. 



This group is represented in New Zealand and Japan. 



Section Dosiniaca Dall, 1902. Type, Artemis (data Reeve. 



Areas of the lunule and escutcheon pouting mesiall}^ defined by a 

 deep sulcus, forming a posterior wing which recalls Phacoide8\ sculp- 

 ture of fine, rather distant, tiiarp lamellae, sometimes with radial stria- 

 tion; pallial sinus deep and lingular. 



This group is distributed in Australia and Japan. 



Section D<mnorhk Dall, 1902. Type, ArteituH Ijllunulata Gray. 

 Japan. 



Lunule and escutcheon deeply impressed, the former surrounded by 

 a larger area bordered as is the escutcheon by a lamellated keel; valves 

 compressed, beaks produced, sculpture on the middle of the disk 

 obsolete, becoming lamellas laterally; pallial sinus short, angular; 

 right posterior margin grooved beyond the hinge plate, to receive the 

 beveled edge of the opposite valve. 



Thi.*- large and remarkable species appears to be unique in the genus. 

 In the young the dorsal margins pout on each side of the ligament. 



Section Dosliildia Dall, 1902. Type, Venus concentriea Born. 



Valves, suborbicular, subcompressed, white, with a sculpture of 

 concentric grooving, never lamellose, furnished with an obvious peri- 

 ostracum; lunule small, impressed; escutcheon absent; pallial sinus 

 ample, ascending, angular in front; posterior cardinals serrate or cor- 

 rugated in the nepionic young, smooth in the adult. 



This group is confined to the tropical and warmer temperate seas of 

 America. 



Section Dosinella Dall, 1902. Type, Oytherea angulosa Philippi. 

 East Indies. 



Valves suborbicular with a shallow flattish lunule; the escutcheon 

 narrow, flattish, hardly defined; pallial sinus ample, ascending, deep, 

 blunth' rounded at the anterior end; anterior lateral and posterior right 

 cardinal teeth absent or obsolete. 



There are a few small species in which the bight of the pallial sinus 

 is rounded, but in this large form the contrast between the blunt 

 rounded form and the angular form usual in the genus is so marked 

 that, after some hesitation, taking the obsolescent hinge-teeth into 

 consideration, it seemed advisable to separate it sectionally. 



Proc. N. M. vol. xxvi— 02 24 



