The byssal gland is quite extensive and not only permeates 

 a considerable portion of the foot but extends some distance 

 dorsally and posteriorly ventral to the retractor muscle of the 

 foot. It is a racemose gland of the usual character. 



ALIMENTARY CANAL. 



The oesophagus is rather short and extends from the mouth, 

 which lies beneath the anterior protruding portion of the liver, 

 to the antero-dorsal portion of the stomach. The stomach 

 fig. 12, s.), is fairly large and receives two large ducts from 

 the liver which surrounds it. The openings of these ducts into 

 the stomach are so large as to form two latteral diverticula of 

 the stomach into which the smaller ducts from the liver empty. 

 The portion of the alimentary canal that extends from the 

 rounded stomach to near the posterior portion of the body is of 

 greater diameter than the remaining portion and resembles in 

 microscopic appearance the . stomach rather than the intestine. 

 A portion of the lining epithelium of this and of the lower end 

 of the stomach resembles that usually concerned in the forma- 

 tion of a crystalline style. While a definite, well formed rod- 

 like style, such as is so well formed in the soft clam, Mya, is not 

 present, a large quantity of mucous is secreted. This mucous 

 entangles the food that is swallowed and very likely performs 

 the same function that is performed by the dissolving of the 

 crystalline style which Kellogg (14) with much reason thinks 

 may be to keep the cilia of the alimentary canal from forcing 

 the food through the canal before it has had time to digest. 



The remaining portion of the alimentary canal, is of about 

 even diameter throughout its length and is lined by epithe- 

 lium of the character ordinarily found in this portion in lamelli- 

 branchs. It is a ciliated epithelium, the cells of which stain 

 deeply and probably have some secretory function. Undoubt- 

 edly the chief reason for having the canal so elongated is to give 

 time and surface for absorbing digested food. 



The position of the loops of the intestine are shown in figure 

 12, i, and needs no special description. It is worth noticing 

 that the loops are practically in the same position in Pecten irra- 

 dians, the only other species of scallop that I have examined. 

 In the figure given by Pelseneer, which is copied in Parker & 



19 



