52 NILS HJ. ODHNER, STUDIES ON RECENT CHAMIDAE. 



fore arriving at the axis. In the corresponding manner all the arterial vessels de- 

 bouch into the branchial arteria, but their distal ends in the upper part of the re- 

 flected lamina are obliterated and only in the lower portion of the gill do there 

 exist any direct Communications between them and the branchial arteria. No con- 

 nections corresponding to those vve met with in Echinochama and appearing between 

 the marginal vein and the vena branchialis exist at all; the latter vein irrigates 

 exclusively the posterior gill, which is effected according to the same scheme as in the 

 species mentioned, but with the difference that in Ch. juJcesi the descending lamina 

 of the posterior gill is also completely furnished with veins as well as arteriae. The 

 veins of this lamella, however, are not differentiated from the marginal one, both 

 being represented in each fold by a single large vessel which has a somewhat cup- 

 shaped dilatation and which forms by its inner margin the intermarginal connection 

 and by its outer one the filamentar vessel (ef. fig. 60). 



The nephridia (figs. 61 — 64) are situated symmetrically at the sides of the 

 intestine; the left one is somewhat larger and higher. They emerge with their 

 funnels from the lateral corners of the pericard, which is narrowed inferiorly so as 

 to be retained only in these corners. Behind the comparatively short nephridial 

 funnels the pericardial tubes of the kidneys widen into a pair of ampullae with 

 folded walls. These lie close to each other and are, for a short space, left uncovered 

 on their upper sides by the outer sacs. After their divergence they are displaced 

 on the rear side of the nephridia and separated from each other by some large lobes 

 of the outer sac. Here they become rather narrow. They open in the upper part 

 of the outer sacs rather remote from their upper ends. The exteriör sacs of the 

 kidneys are wide and lobated into large and spacious follicles, have a narrow com- 

 munication above the nephridial funnels and open on the outer side of these opposite 

 the genital pores. 



In a young stage (length of the shell 3 mm) the nephridia (fig. 63) were dif- 

 ferent from those of the adult in having completely separated pericardial tubes, 

 which were situated on the under and hinder sides of the outer sacs and completely 

 embedded in these. 



No trace of foot retractors was observable in either the young or the adult 

 stage. 



The genital organs consist of tubes with many branches; in the adult spe- 

 cimen that was examined microscopically they contained eggs. They debouch through 

 a pair of short ciliated papillae situated in front of and close to the nephroprocts 

 but somewhat higher up than these. 



Chama sarda Reeve. 

 Fig. 65. 



Of this species, from the West Indies, two specimens were examined in sec- 

 tions and some others in toto. 



