1867.] Contributions to Indian Malacology. 57 



strongest. Those near the suture, both above and below, are less strong- 

 ly marked, and are occasionally obsolete. On the last whorl the up- 

 permost ridge near the suture is alone fainter than the others* The 

 body whorl ascends a little towards the aperture, which is subvertical 

 and nearly elliptical. The anterior canaliculation is obsolete in the 

 adult, but it is well marked in the young shell. Peristome much 

 thickened, externally variciform, the varix being nodose in consequence 

 of the spiral ribs of the body whorl being continuous upon it. In 

 young specimens the lip is grooved inside, the grooves corresponding 

 to the external ribbing, and slight remains of this grooving may be 

 traced in the adult shell. 



I had at first classed this shell as a Rissoina on account of the 

 obsolete canal, although it differs in essential characters from any 

 species of that genus. I am indebted to my friend Dr. Stoliczka for 

 calling my attention to the great distinctions which exist between the 

 present form and Rissoina, and some of which equally serve to dis- 

 tinguish it from Rissoa and all other genera of the group. Iravadia 

 differs from Rissoina in possessing an epidermis, in having spiral 

 sculpture, in the peristome neither being sinuate above, nor projecting 

 below, and in; the columellar margin being simply curved in front and 

 not excavated. From Rissoa it is distinguished also by its epidermis and 

 sculpture, by the obsolete channel in front of the aperture, which, in 

 young specimens, is quite as distinct as in Rissoina, and by the ab- 

 sence of any tendency to the columellar tooth or fold, which is so con- 

 spicuous in the typical species of the genus. The characters of the 

 sculpture, epidermis, and aperture serve equally to separate the 

 present form from Alvania, Onoba, Geratia and other genera of 

 RissoidcB : Hydrobia and Amnicola alone have an epidermis, but both 

 are smooth shells without a variciform peristome. 



It is unfortunate that no specimen of the operculum has been pre- 

 served. The few shells found were collected during a hurried journey 

 in a boat. The species was only met with at one spot, under stones^ 

 amongst some rocks in a creek leading into the Myittaya, a branch of 

 the Bassein river. Several specimens were obtained, but when an 

 opportunity was afforded of examining them at leisure, the opercula 

 had disappeared. In the absence of the operculum, I should be dis- 

 posed to consider the genus as more nearly allied to Rissoina than to 



