48 Mr. J. W. Williams on a neio Species o/" Ampullaria. 



and its breadth (taking the body- whorl) 48 millim. The 

 general shape of the shell is globoso-conoidal, the body-whorl 

 in the region of the peritreme being considerably swollen, but 

 compressed laterally in that part where it passes into the 

 penultimate whorl. There are five whorls. The spire is 

 very short (12 millim.) in comparison with the rest of the 

 shell, and its apex is obtuse. The suture between the body 

 and the penultimate whorl and also between this last and the 

 antepenultimate whorl is deeply and triangularly channelled 

 (hence the specific name of canaliculata proposed for it) . The 

 nucleus is of a light rufous colour. The general body-colour 

 is of a dull yellowish green (similar to that of our English 

 Paludina vivijjara, Linn.) and is marked on the body-whorl 

 by fourteen linear brown spiral bands, by four on the penul- 

 timate, and by three on the antepenultimate whorl. The 

 periostracum is strongly marked with closely placed longitu- 

 dinal striiB continuous from whorl to whorl over the sutures ; 

 the transverse striai are much finer and wider apart than are 

 the longitudinal stria?. The inner lip is reflected upon the 

 body-whorl, and behind a ledge of it can be seen a large, 

 deep, and obliquely placed umbilicus. The aperture is of an 

 ovoidal shape, with a transverse diameter of 34 millim. and a 

 longitudinal one of 45 millim. The peritreme is of a car- 

 neous colour, and this is continued on the inside of the body- 

 whorl for a distance in one specimen of 14 millim., behind 

 which the internal layer of the shell is coloured a chocolate- 

 brown. The banding of the shell is visible on looking into 

 the shell from the aperture. The operculum is chitinous (as 

 is the case with nearly all New-World species) and somewhat 

 of a reniform shape, its narrower end being placed in the 

 aperture upwards. It is well marked by concentric striae and 

 the nucleus is placed excentrically, near to what corresponds 

 to the hilum of its reniform shape. On its outer aspect the 

 nucleus is placed on a depressed area, which corresponds to 

 a circumscribed elevation on its inner aspect. The whole of 

 the periostracum is glossy and the whole shell translucent. 

 The umbilicus discloses a part of the penultimate whorl. 



The specimens from which I have given the above descrip- 

 tion were collected by Mr. George in October last. They were 

 sent to me on May 8th of this year, having been brought by 

 him from Buenos Ayres, and the most interesting part of it 

 is that one of the shells contained an animal which, on extrac- 

 tion, showed evidence of very recent death, and which, 

 although giving otT no fetor, was unfortunately not quite in a 

 fit state for systematic dissection. Mr. George brought the 

 shells over packed with Unios and Helix [Macularia] punctata^ 



