38 NILS HJ. ODHNBR, STUDIES ON RECENT CHAMIDAE. 



Pseudochama exogyra Conrad. 



Figs. 33—37. 

 Three specimens from California have been examined, one of them in sections. 



External morphology. 



Mantle (fig. 33). Its edge is shortly papillated above and between the siphonal 

 openings, which occupy together more than V3 (nearly ?,) of the inferior margin (from 

 anterior to posterior adductor). Pedal slit small, immediately beneath the anterior 

 adductor; in front of this the mantle is open. There is no siphonal fold beneath 

 the expiratory opening. The right umbonal process is made up of the thickened 

 mantle throughout and contains no liver diverticula nor any genital coeca. 



The anterior adductor is about equal in length to the distance between the 

 upper ends of the adductors and is larger than the posterior one (which is about 

 2 /3 of the former). 



The labial palps are situated at unequal heights, the anterior one of the left 

 side with its anterior corner as high up as the upper end of the adductor and the 

 apex at about l /t of its length; on the right side the palps are thrown upwards 

 so that their ends do not reach the adductor; besides that they are directed back- 

 wards. Both pairs are connected by lips and striped on their adoral sides. 



A finger-shaped f oot projects towards the pedal slit. Its length is about 3 — 

 4 times its breadth and about x Ja (nearly J) of the inferior margin from anterior to 

 posterior adductor; the body behind the foot is rounded and somewhat depending, 

 with or without an inconspicuous triangulär lobe situated at a distance from the foot 

 equal to the length of the foot. 



The gills häng freely, separated from each other and from the mantle ; the 

 upper edges of the reflected plates in both gills are free from the body. At the 

 mantle the anterior edge is somewhat retracted, leaving the labial palps uncovered 

 by the gill. 



Intcrnal anatomy. 



Intestinal system (fig. 34). No common liver canal exists; on the left side 

 of the stomach opens only an ordinary small one, on the right side many large ones 

 debouch, especially a rather wide one in the posterior part of the stomach. From 

 the posterior wall of the stomach there emerges a short coecum that descends to 

 about the cerebro-visceral connective. In the duodenum the narrower furrow lies 

 in front or somewhat to the right, the broader one at the hinder side. By taking 

 a turn forwards and upwards the duodenum passes into the intestine, which is 

 somewhat widened before it attains its rectal portion. 



