62 NILS HJ. ODHNER, STUDIES ON RECENT CHAMIDAE. 



level, the right only a little more anterior than the left one. They are connected 

 by a short commissure (its length equalling that of a single ganglion). Buccal ganglia 

 are quite distinct and situated as usual. Pallial nerves are distinct on both sides. 

 Of the cerebro-visceral connectives the right one penetrates the liver throughout its 

 vvhole extent and passes nearer to the duodenum than to the surface of the body; 

 the left one is subcutaneous outside the duodenum and the intestine. A median 

 commissure exists between them in front of the pericard. 



The gills. Each fold contains about 50 filaments in the inner demi-branch 

 and above 60 in the outer one of the anterior gill. In the posterior gill the descend- 

 ing lamella is also folded but is narrow, being only 1 jz of the outer one in breadth. 

 In this latter lamella about 50 filaments compose one fold. Direct intermarginal 

 connections exist in the lower part of the gill below the point of entrance of the 

 vena branchialis into the axis of the gill. Interfoliar connections are established 

 only between the venous principal filaments; the arterial ones are united only near 

 the frontal margin. 



The nephridia. These are of about equal form and size, situated behind the 

 pericard, which is to a great extent open, and extend upwards to the sides of the 

 rectum, where they terminate at the same height. The one on the right side is 

 somewhat wider. The narrow pericardial tubes open into the upper part of the 

 outer sacs, at about the upper third of their height, where they are completely 

 embedded in the middle of their back walls. Below they widen into a pair of length- 

 ened and somewhat ventrally expanded ampullae with slightly folded walls and are 

 completely separated from each other in the median line by the intrusion of lobes 

 from the outer sacs. The pericardial tubes open into the pericard through short 

 and wide oscular funnels, the length of which does not exceed the breadth of the 

 interjacent space. They diverge only slightly and are produced in the same direction 

 as the ampullae. Above the ampullae a narrow communication exists between the 

 outer sacs. Their external apertures are seen just below the nephrostomes as a 

 narrow fissure with somewhat thickened lips. 



The foot retractors are observed as rather strong cords on the back sides of 

 the ampullae and their continuations upwards. They reach the adductor and insert 

 the shell in front of it. 



The genital openings form wide fissures with slightly produced margins 

 situated in front of and somewhat above the nephrostomes. 



Chama pellucida Broderip. 



In order to test the statements made by Grieser (1913) as to the position 

 of the stomachal coecum and the duodenal furrows in Ch. pellucida, I sectioned a 

 specimen from St. Joseph, Panama (collected by the Eugenie Exp. in 1852). Though 

 badly preserved it showed distinctly a narrow coecal appendage emerging from 

 the lejt side of the stomach and extending straight forward to the side of the oe- 



