MORPHCiLOGY OF THE HELICIXID^. 771 



fesopliagus. Botli the oesophageal aperture and those of the liver- 

 ducts aie surrounded by complicated epithelial ridges, which, as 

 shown in the drawing, converge towards and pass into a deep 

 groove running along the dorsal side of the narrower pyloric 

 moiety of the stomach. The edges of this groove are bounded by 

 two prominent folds ; that on the right side (the left in the 

 di'awing) being continued towards the oesophageal opening as a 

 projecting ridge, ending at the side of the aperture in a very 

 prominent crescentic projection covered by a thick iridescent 

 cuticle. 



The internal surface of the stomach Ls lined by a mixed glan- 

 dular and ciliated columnar epithelium, the characters of which 

 are shown in PI. XXXI. fig. 8 ; the glandular elements predominate 

 in the oesojjhageal, the ciliated elements in the pyloric, moiety of 

 the stomach. The epithelial cells are lower in the furrows, taller 

 and more slender in the ridges, these latter structures being 

 formed entirely by thickenings of the epithelium, and not by 

 foldings of the wall of the stomach. The cre.scentic projection to 

 the right of the oesophageal opening is formed by a local modifi- 

 cation of the epithelium, the cells of Avhich are here extraordi- 

 narily long, with nuclei placed about the middle of their length, 

 and with apparently homogeneous transpjarent cytoplasmic contents 

 (PI. XXXT. fig. 9) ; they are all of one kind, without any admix- 

 ture of glandular cells, and, so far as one can judge, they are not 

 themselves glandular. The free ends of these cells are covered by a 

 very thick and tough cuticular coat, which stains deeply in haema- 

 toxylin, brazilin, and other ordinary dyes. Tlie whole structure 

 corresponds to the " fleche tricuspide," of which the characters 

 have been thoroughly described for Lamellibranch stomachs, 

 and which has been noted as occurring in several (gastropod 

 'stomachs. There is no definite crystalline style in Helicinidse, 

 but in several specimens that I dissected I found the cavity of 

 the stomach filled by a semitransparent gelatinous mass, which 

 appeared to be similar in origin and composition to a crystalline 

 style. In several specimens I found that the intestinal end of 

 the groove of the pyloric moiety of the stomach wa.s occupied by 

 closely compacted fa'cal pellets or rods, while the cavity below 

 was filled either by the gelatinous mass above mentioned or by a 

 loose mass of semi-digested food. It may be inferred from this 

 that digestion is efi'ected in the general cavity of the stomach, 

 and that the indigestible materials of the food are collected into 

 the dorsal groove and passed into the intestine. 



Morphologically, the .stomach of the Helicinidse closely resembles 

 that of the Xeritidte, and fuiiiher bears a resemblance to the 

 stomachs of the Fi-ssurellidse and Scissurellid*, which, as in this 

 case, have a groove leading from the hepatic ducts towards the 

 intestinal end of the .stomach, but no spiral csecum. 



The small intestine is a comparatively narrow tube, which after 

 leaving the pyloric end of the stomach r\ins back for a short 

 distance over the dorsal surface of the latter, parallel with the 



