[ 307 ] 



VIII. Iteport on the River-Crahs [Potamonidce) collected hy the British Ornithologists' 

 Union Expedition and the Wollaston Expedition in Dutch New Guinea. 

 By W. T. Calman, B.Sc, F.Z.S. * 



[Eeceived February 17, 1914 ; Read April 7, 1914.] 



(Text-figures 12 & 13.) 



Index. 



Page 

 Potamonidse (Bracliyura, Cyclomefcopa), affinities of some Malaysian species . . 307 



Paraihelplmsa {LioteJpliusa'i) aruana (Eoux) 308 



„ ,, ivollastoni, sp. n., Utakwa Pdver 310 



„ „ plana, sp. n., Utakwa River 311 



The freshwater Decapod Crustacea obtained by the two expeditions consist of nine 

 Crayfishes, seventeen Eiver-Crabs, and one mutilated and indeterminable Palsemonid. 

 The Crayfishes have been reported on elsewhere f, and the River-Crabs form the subject 

 of this paper. Thirteen of the specimens are referred to a species recently described 

 by Dr. J. Eoux from the Aru Islands, of which, by the kindness of Dr. Roux, I have 

 been able to examine a co-type ; and two species are described as new, each from a 

 pair of specimens. 



It is somewhat difficult to decide what generic names ought to be applied to 

 the various species, according to the more recent schemes of Potamonid classification. 

 All the species have the mandibular palp bilobed, the male abdomen considerably 

 narrowed, with the sixth somite longer than wide, or only a very little shorter, and 

 the telsou tongue-shaped. They can, therefore, be referred, without any doubt, to 

 Alcock's subfamily Gecarcinucinse. Their position within the subfamily is, however, 

 not so clear. In all of them the front is wider by at least two-thirds than the 

 orbit, the subterminal tooth on the upper border of the merus of the chelipeds is in 

 most cases acute or spiniform, and the postorbital crests are obsolete. According 

 to Alcock's synopsis of the Gecarcinucinaj ;]:, therefore, they should be referred to 

 the genus (or subgenus) Peritelphusa, from the other species of which, however, 

 they differ in the great reduction of the epibranchial tooth. If, on other hand, the 



* Published by permission of the Trustees of the British Museum, 

 t Ann. Mag. Nat. Hist. (8) viii. 1911, pp. 366-368. 

 i Rec. Indian Mus. v. 1910, p. 259. 



VOL. xx. — PART VIII. No. 1. — Hay, 1914. 2 u 



