1921.] Manipur Molluscs. 591 



resembles that of A. (F.) verruca, but the central piece is larger 

 and more compact, while the lateral pieces are fewer but larger. 



A short but capacious oesophagus leads to the stomach, which 

 is divided into three regions by a very stout band of circular 

 muscles. This band, which is interrupted on the lower surface, 

 forms a kind of gizzard and when constricted gives the lumen of 

 tde stomach an hourglass-shape. The intestine has a precisely 

 similar course to that of A. fluviatilis as figured by Simrotb,' 

 but we could not see any processes, in our dissections, at the 

 point where the intestine leaves the stomach ; Simroth shows 

 them as well developed in A. fluviatilis. The anus is situated a 

 short distance behind the base of the left tentacle. 



The genital pore is situated immediately in front of the anus. 

 The genitalia are imperfectly preserved in our material but the 

 female system seems to have been better developed than the male. 

 The hermaphrodite gland is full of large ova. The penis is short 

 and papdliform and a flagellum is present, but considerably shorter 

 than in Ancylus fluviatilis as figured by Simroth {op. cit., pi. 

 xxvi_. fig. II). 



The kidney is large and occupies the anterior part of the 

 branchial cavity. 



The edge of the mantle bears numerous minute conical retrac- 

 tile bodies that do not seem to be of parasitical origin. 



Type- sped men. — No. M 11718/2 Zool. Surv. Ind. (Ind Mus.). 



Localities, etc. — This species was found in abundance with 

 Camptoceras lineatmn on the lower side of floating grass-stems in a 

 small, sluggish muddy stream running into the north end of the 

 I<oktak Lake, Manipur, in February, 1920. It was also taken in 

 the same situation in a small muddy pond at Dimapur in the 

 plains of Assam just north of the Naga Hills. 



The stomach is full of mud containing the tests of numerous 

 diatoms. The animal moves rather quickly on a smooth surface 

 and can float shell-downwards just below the surface-film of the 

 water. 



Affinities.— The shell closely resembles that of A. (F.) tenuis, 

 Bourg., from South India but may be distinguished by its brilliant 

 internal colour and fine but distinct sculpture. 



Ancylus (Ferrissia) ceylanicus, Benson. 



1S76. Ancylus ceylanicus. Hanley and Theobald. Condi. Ind., pi. lxx<i. 

 tigs. I and 4. 



Among a number of specimens of .4. (F.) verruca from a pond 

 in Imphal we find a single shell that agrees closely with the figures 

 of A. ceylanicus in the Conch. Indica, which may probably be 

 taken as a correct representation of this species. This specimen 

 is 6 mm. long, 4 mm. broad and 2"5 mm. high. 



I Bronn's Thier-Reichs III (Supplement), Mollusca, p. 338, fitf. ri3A (ign). 



