llO Records of the Indian Museum. [Vol. XIY, 



ventral aspect ; in the latter it occupies only one tenth of the length of 

 the shell. It consists of two whorls, which are neither shouldered nor 

 markedly tumid. The suture is not or hardly impressed. The body- 

 whorl is ovate, elongate and narrow ; its lateral outlines do not project 

 far beyond those of the base of the spire ; its anterior internal margin is 

 broadly rounded, its anterior outer margin angulate and a little pro- 

 duced. The aperture is almost straight, narrow, elongate and practi- 

 cally lanceolate in outline. Posteriorly it tapers gradually to a fine 

 point and in front it is angulate externally. The peristome is simple, 

 the rimate margin of the orifice distinct but delicate. The columella 

 is almost concealed ; it is nearly straight and slopes forwards and out- 

 wards. Its callus is feebly developed. 



The animal is that of a typical Limnaea. The foot is very exten- 

 sible but can be retracted well within the shell. The tentacles are 

 short. The whole external surface is white or greyish, with black eyes 

 and an effusion of black pigment on the dorsal surface of the body and 

 on the mantle. The specimens examined are sexually mature. A figure 

 of the genital system, dissected out and drawn for me by Dr. Baini 

 Prashad of the Bengal Fishery Departnicnt, is reproduced on p. 175 of 

 this paper. It seems quite normal, bui, all the parts are slender as 

 compared with those of European and American species. The sper- 

 niathecal duct is long and the penis-sheath stout. 



The jaw resembles that of L. howelli, but is much less produced. 

 The radula (pi. xi, fig. 4) is also similar, but the cusps of the lateral 

 teeth are more nearly equal and equidistant and the marginal teeth 

 (except at the extreme edge) have four instead of three cusps. 



mm. 

 Length of shell ... ... ... ... ... 6 



Greatest breadth of shell ... ... ... ... 2-5 



Length of aperture ... ... ... ... 4-25 



Greatest breadth of aperture ... ... ... ... 2 



Type-specimen. No. M. 11271/2, Zoological Survey of India {Ind. 

 Mus.). 



The species is probably but the final stage in a line of evolution 

 similar to that of the phases of L. shanensis (pi. x, figs. 4-8). It 

 may be no more than an extremely degenerate phase of L. acuminata,'^ 

 Linn. 



L. mimetica lives amidst dense growing vegetation both in the 

 intermediate zone and the central region of the Inle Lake, but probably 

 avoids the extreme edge. It is not uncommon but nowhere abundant. 

 Individuals from the intermediate zone have both shell and soft-parts 

 darker than those from the open lake. 



In general appearance the shell bears a very striking resemblance 

 to that of Succinea indica, a mollusc not uncommon at the edge of the 

 Inle Lake, but one that does not live submerged. The shell of this 

 semi-terrestrial species differs from that of the Limnaea in its much 



^ The upper jaw of L. acuminata is not jjroduced in front, but the radula is very like 

 that of L. mimetica. I am not convinced that the shape of the jaw is constant. 

 Moreover, the radular teeth are subject to minor variations in shape. 



