KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 59- N:0 3. 39 



The blood system. The upper branch of the anterior aorta gives off a vessel 

 to the mantle and passes to the left of the stomach and downwards on the left 

 side of the oesophagus, and a small branch runs över to its right side; behind the 

 mouth it gets a median position and runs down into the foot. The descending trunk 

 of the aorta passes on the left side to the stomach under the coecal appendage, 

 where it divides and surrounds the stomach; from the base of this trunk a small 

 lateral vessel is given off to the right side of the body. 



The nervous system is similar to that of Echinochama arcinella in having a 

 distinct buccal ganglion on each side. The cerebro-visceral connectives pass through 

 the liver nearer to the stomach than to the outer surface of the body; the right 

 one lies almost immediately outside the stomach. Statocysts were easily seen at the 

 sides of and somewhat above the pedal ganglia. 



The gills are folded, as usual, and each fold contains about 28 — 30 filamen ts. 

 Otherwise the gills are constructed according to the same scheme as in Echinochama, 

 but the interfilamentar bridges are not situated so densely as there, there being 

 about 30 altogether in a single fold. There are also, as in Echinochama, direct 

 axio-marginal junctions between the veins in the lower part of the gills. 



The ge ni t al organs offer nothing of especial interest, their exteriör openings 

 lie at about the same level as the nephrostomes; they are wide, and each is pro- 

 longed into a papilla. 



Nephridia (figs. 35 — 37). The intestine passes about medially through the 

 heart and above the adductor, and the nephridia, consequently, are situated sym- 

 metrically. The right one rises somewhat higher than the left, but both terminate 

 below the intestine. The pericardium is open and symmetric throughout and not 

 much compressed in an antero-posterior direction. The nephrostomes are placed 

 rather close to each other in the lateral corners of the pericard. The ciliated funnels 

 are rather short, though broad ; they converge inwardly, and behind them the peri- 

 cardial tubes approach closely; each widens to an ampulla-shaped organ with folded 

 walls, and both lie pressed closely upon each other. Backvvards and upwards the 

 pericardial tubes grovv somewhat narrower again and ultimately debouch into the 

 uppermost parts of the outer sacs, on their posterior side. The last-named form 

 numerous small pockets in their walls, communicate by a short passage with each 

 other immediately above the ciliated funnels and debouch outside and below the 

 nephrostomes, opposite to the genital pores. Through the outer sacs there pass the 

 foot retractors in a ventro-dorsal direction and at the bottom of deep furrows which 

 penetrate from below and divide each sac into two large lobes (ef. figs. 35, 37). 



Pseudochama ferruginea Reeve. 



Figs. 38—45. 



Some specimens from the West Indies were examined, one of them being 

 rather young, only 3 mm in length. One of the examples was sectioned. 



