KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 59. N:0 3. 33 



breadth (in one specimen; in the other it is somewhat shorter, with a more con- 

 tracted opening). Its margins are extremely finely papillated. 



The adductor muscles are about uniform in size; the distance between their 

 upper ends is greater than the length of the anterior one, which has a concave 

 anterior outline. 



The labial palps are elongated, triangulär, with rounded ends, and attached 

 at an equal height on both sides, somewhat below the upper end of the adductor; 

 their length is about a third of that of the adductor. On their oral side the palps 

 have up to 13 ridges, each accompanied by a secondary one. Congregations of 

 unicellular glands are, as usual, present in their interiör, appearing externally as a 

 branched or dendritic pattern of pigmented veins. Cuénot, who has studied (1914) 

 these formations in Solen, finds in them a kind of phagocytic organs, which seem 

 to be comraon among the Lamellibranchs. 



The foot is elongated, vermiform, its length being about 5 times the breadth, 

 and it projects about half-way between the mouth and the lower end of the visceral 

 hump. Behind the foot there follows a triangulär pouch of the visceral hump with 

 a very small triangulär lobe situated behind at a distance from the end of the 

 pouch equal to the distance from this to the base of the foot. 



The gills leave the front half of the body uncovered. The posterior gill is 

 somewhat more than half as broad as the anterior one. Both gills are (in both 

 specimens) completely free from each other and from the mantle, with their ends 

 hanging within the siphonal fold. Their reflected laminae are attached to the body 

 only in their upper part (to a longer or shorter extent). 



Intemal anatomy. 



The intestinal system (fig. 29). The oral orifice is broad, and the oeso- 

 phagus has, in the beginning, a triangulär section with small lists projecting in- 

 wardly. Higher up its shape becomes more flattened (oval in transversal section), 

 and its epithelium is considerably low and the walls lose their folds. (No further 

 details could be stated because of the bad state of preservation.) Towards the 

 stomach the oesophagus widens, its epithelium becomes more elevated and there 

 appears a minute plication of it in a longitudinal direction. Dorsally the oesophagus 

 curves up to a level higher than the stomach. 



In its upper portion the stomach is rather wide; it is protracted into a small 

 corner backwards. Its frontal walls are like those of the oesophagus, b ut the back 

 ones are lined with a thick cylindrical epithelium. From the posterior right side 

 there projects a pouch of the wall which, farther below, is separated from the sto- 

 mach, forming a sort of coecum with a large transversal extension. From the frontal 

 wall, to the left of the oesophagus, the large Ii ver duct emerges; it is directed down- 

 wards and is comparatively narrow and short, and did not contain any nutritive 

 substance in the case of the specimen examined. Other liver ducts debouch both 



K. Sv. Vet. Akad. ITandl. Band 59. N:o 3. 5 



