296 Records of the Indian Museum. [Voi,. VIII, 



bright red colour, averaging 2*4 X 2 mm. in longer and shorter 

 diameter. 



P. aborense appears to be rare in the Abor country, but as all 

 the specimens were found under stones in dry situations it may be 

 that the species has habits different from the majority of forms 

 obtained in the country and this perhaps accounts for its apparent 

 scarcity. 



All three type-specimens come from the vicinity of Rotung at 

 altitudes of between 1000 and 1300 ft ; one Cu^) was found at no 

 great distance from the Egar stream ; another, the ovigerous fe- 

 male (^), was taken in March from a short burrow with a slightl}' 

 enlarged terminal chamber behind a large stone on a steep hill- 

 side; the remaining example was obtained by Capt. de Courcy 

 when cutting a road between Rotung and the Sireng stream (^). 



Potamon (Potamiscus) obliteratum, sp. nov. 

 (Plate xviii, figs. 9, 9a.) 



I take this opportunity of describing a very fine species of 

 Potamiscus obtained recently by Mr. F. H. Gravely in the Dawna 

 Hills. In most cases I would hesitate to give an account of a 

 species of Potamonid represented, as in the present instance, only 

 by a single individual ; but the specimen is in several respects 

 highly peculiar and this fact, together with the circumstance that 

 two other new species of the sub-genus are described in the present 

 paper, may perhaps be held to justify its inclusion. 



The individual is a female with the carapace 19 mm. long, 23"5 

 mm. broad and 13 mm. deep; it is thus proportionately slightly 

 deeper even than in P. aborense. The carapace (fig. 9) is strongly 

 and evenly convex fore and aft and slighth' so across its greatest 

 breadth, and everywhere on its dorsal surface it is rather coarsely 

 pitted. 



Seen from above it is very noticeably quadrate in shape. The 

 sides of the carapace are, indeed, less convergent posteriorly than 

 in the allied species ; but the principal reason of its square appear- 

 ance is that the postero-lateral portions do not slope away ob- 

 liquely to the bases of the last two pairs of walking legs, as in P. 

 sikkimense and aborense^ but are inflated and have the lateral 

 walls abruptly declivous. 



The antero-lateral portions of the carapace are strongly rugose 

 and a number of prominent ridges and tubercles obscure the post- 

 orbital and epigastric crests. The frontal surface in advance of 

 the latter is sharply tuberculous. 



The cervical groove is deeply cut where it defines the posterior 

 part of the mesogastric lobe and with its lateral backward continu- 

 ations forms a well-defined figure in the form of an H . The course 

 of its anterior branches towards the post-orbital crests can onh' be 

 traced with great diihculty. 



