1921.] Manipur Molluscs. 597 



structures open into it. These are the so-called seminal vesicles : 

 they have thick muscular walls, and a narrow lumen containing 

 spermatozoa. The hermaphrodite duct at this place swells up into 

 a small pouch called by Ihering {loc. cit.) the fecundation pouch. 

 Its internal walls are thrown into complicated folds. On its exit 

 from the albumen gland the hermaphrodite duct is continued as 

 the uterus on one hand, and the male duct on the other. 



Taking first the female elements, we find the uterus descend- 

 ing in numerous coils. Its walls when immersed in water assume 

 a transparent gelatinous appearance. Distally it is somewhat di- 

 lated and at the point of its junction with the duct of the recepta- 

 culum seminis becomes considerably contracted. It is then con- 

 tinued forwards as a muscular vagina. The receptaculum seminis 

 is subcircular and has a long slender duct. The vagina is short 

 but thick. 



The male duct on its exit from the albumen gland bears im- 

 mediately a rather large, elliptical gland, the prostate, which lies 

 on the right side below the uterus. The vas deferens runs close to 

 the inner side of the vagina and at the point where vagina and penis 

 meet together, it turns up sharply, and, running internally to the 

 walls of the penis-sac, opens finally at the tip of the penis. The 

 penis is a thick muscular organ, the internal walls of which are 

 thrown into complicated folds and are glandular. The penis-sheath 

 is thin and consists mainly of longitudinal muscle-fibres. The re- 

 tractor muscle is attached close to the point where the vas deferens 

 enters the penis. 



The male and the female ducts open separately into the short 

 common atrium, which communicates with the exterior by a nar- 

 row slit-like aperture. 



The Alimentary System. — The mouth is situated on the lower 

 surface of the extreme anterior 

 end of the snout and is bounded 

 by fleshy lips. The buccal-sac is 

 thick and globular. 



The jaw is black and stout. 

 Its cutting edge is broadly con- 

 cave and has a rounded projec- 

 tion in the middle. The acces- 

 sory plate is rounded posteriorly 

 and quite broad. The radula is a. t,-,^ ,,._jaws of Succinea elega,:- 

 broad ribbon and has approxi- tior, Annandale. 



mately the formula 40.(10-12).!. 



(10-12). 40. The central tooth has a greatly developed median cusp 

 but the side cusps are sub-obsolete. Its base is horizontal and 

 slightly concave. The margins of the basal discs are thickened or 

 probably folded in, so as to form a vertical ridge on each side. 

 They disappear on the upper part of this resiion of the tooth. The 

 laterals are tricuspid, the inner cusp being l.ng and nearly reaching 

 the base. Their bases are not horizontal but obliquely truncate, 

 the inner angle being at a considerably higher level than the outer. 



