246 Records of the Indian Museum. [Vol. Ill, 



one-fourth the greatest 1)readth of the carapace — and is vertically 

 deflexed. 



A single female, with a carapace nearly 2 inches broad, from 

 Burma. 



14. Potamon {Potamon) pruinosum^ sp. nov. 



Belongs to the P. lariiaudii clan, but differs from this and all 

 other related species in the profusely tuberculous carapace. The 

 carapace is deep — its depth equals half its length — and its grooves 

 are very faint. The cervical groove does not cut the post-orbital 

 crests. The surface of the frontal and of the anterior half of the 

 gastric and epibranchial regions is covered with pearl}^ granules and 

 transverse dentiform tubercles of a brilliant whitish colour. Smaller 

 pearly white granules stud the chelipeds. The edge of the epigas- 

 tric and post-orbital crests is broken into long transverse and 

 oblique whitish imbricating tubercles. Its nearest relative is 

 P. brerimarginatnm , deMan ; but it is more profusely and crisply and 

 finely tuberculous than that species ; has a deeper carapace ; and, 

 except for a ver}^ superficial and incomplete cervical groove, has 

 no distinct areolation of the dorsum. 



Locality. — Hills between Burma and Siam. 



No. 2. 



PoTAMiscus, gen. nov. 



Potamiscus in one particular (namely, the absence of a flagellum 

 from the exopodite of the external maxillipeds) resembles Pseudotel- 

 phusa; but it has no other affinities with that genus. Its closest 

 relations are with the Potamon ftiiviatile group, as it has a simple 

 mandibular palp — i.e., a mandibular palp with the terminal joint 

 not bifurcate — such as is found in P. fluviatile, P. atkinsonianum, P. 

 koolooense , P. andersonianum , P. edwardsi, P. hispidum, P. hifa- 

 rium, P. pealianuni, P. tmnidum, P. iurgidtdum, P. tuniidulum, 

 P. austenianum , P. sinmlum, P. larnaudii, P. manii, P. brevimar- 

 ginatum, P. sioliczkamim, P. thagatense, P. (Geotelphusa) sikkimense, 

 and not in any other Indian species. The value of the mandibu- 

 lar palp in classifying the Potamonidai has lately been disclosed 

 by Dr. W. T. Caiman. 



I. Potamiscus annandalii, sp. nov. 



This species has a very strong superficial resemblance to 

 P. pealianum , from which it is easily distinguished by the following 

 characters : — 



(i) the flagellum of the exopodite of the external maxillipeds 

 is either quite vestigial or altogether wanting ; 



(2) the cervical groove is distinguishable only in the middle of 

 the carapace, vVhere it bounds the mesogastric areola posteriorly; 



(3) the post-frontal and post-orbital crests form a continuous 

 wavy curve from the middle line to the lateral epibranchial tooth, 



