50 NILS HJ. ODIINER, STUDIES ON RECENT CHAMIDAE. 



according to the state of preservation so that it may be, sometimes, broad and 

 short. Behind the freely projecting foot the body hängs like a pouch, and then 

 follows a triangulär lobe, which in most specimens forms the footing of the inner 

 gill lamellae; only in exceptional cases is it free from these. This lobe is larger than 

 the »pouch» and the foot together. 



The gills cover the whole body on the umbones as well; above, behind the 

 labial palps, their margins are somewhat sinuous. In a great number of specimens 

 (22) the gills were attached by their axes to each other behind the foot, to the 

 mantle by their ends and by their inner lamellae to the lobe of the foot as well as 

 to each other. Either both the gills were attached to the body and the mantle 

 by their reflected lamellae, or their respective margins were completely or partly 

 free. Only in a few specimens were the gills free from one another but fixed loosely 

 to the mantle; their reflected lamellae were free and the foot had a long projecting 

 triangulär lobe. The posterior gill of either side or of both sides may be partly or 

 completely free, while the anterior one is attached, but never, it seems, vice versa; 

 the posterior gill is not attached when the anterior one is free. 



The soft parts are quite as variable in their morphology as is the shell in its 

 form and sculpture. In the size of the labial palps and the foot, as well as of the 

 gills a great variation is found (undoubtedly influenced by the state of preservation), 

 and no cases of mutual correlation of the organs can be established with regard to 

 their size. The only case of constancy seems to be present in the relative size of 

 the adductors; their length was about equal in all the specimens examined. 



Internal anatomy. 



The intestinal canal (fig. 57). A large liver canal opens in the median an- 

 terior side of the stomach, receiving abundant branches from both sides. It extends 

 downwards to the height of the mouth. Besides that some other liver ducts de- 

 bouch on both sides of the stomach at about the same height as the primary one. 

 From the uppermost ventricle of the stomach there emerges a coecal appendage 

 extending forward on the left side in a slight curve and ending acuminate and blind. 

 In its interiör it is lined with a high ciliated epithelium. On the back wall of the 

 stomach another short median coecal appendage debouches. The duodenum is divided 

 by two epithelial lists into one narrow right furrow and a more spacious left one. 

 Towards the lower end the foremost list gets the shape of a typhlosolis, the back 

 one disappears. By a single curve the duodenum passes into the intestine, which 

 is somewhat dilated in its median part. 



Compared with Ch. pellucida described by Grieser 1913 the present species 

 shows a reversed construction of the stomach. In Ch. pellucida (ef. Grieser, fig. E) 

 we find a right anterior coecal appendage, and the division of the duodenum is 

 made in such a way that the narrower furrow runs to the left and the broader one 

 to the right. Another considerable difference exists in the presence of a posterior 

 coecum in Ch. julcesi, which seems to be absent in Ch. pellucida. 



