914 DR. W. T. CALMAN ON 



52. On Freshwater Decapod Crustacea (Families Potamoni Jse 

 and Palsemonidse) collected in Madagascar by the Hon. 

 Paul A. Methuen. By W. T. (^lman, D.Sc, F.Z.S.t 



[Received October 8, 1913 : Read November 11, 1913.] 

 (Plates XCI. & XCII.J and Text-figure 161.) 



Index. Page 



Introduction and List of Localities 914 



Part I. Famil}' Potamonidj?. 



1. Description of the Material 915 



Fotamon {Potamon) madagascariense A. Milne-Edwards, 



and its Varietal Forms 916 



Potowjojt (PotejKow) ^OMC^o^j H. Milne-Edwards 920 



Potamon {Potamon) methueni, sp. n 920 



Hydrothelphusa agilis A. Milne- Edwards 922 



2. S^'stematic Affinities of the Madagascar River-Crabs 922 



3. Geographical Relations of the Madagascar River-Crabs 925 



Part II. Family Paljemonid.Ii. 



Palcemon {Macrohrachium) lejpidactj/lus Hilgendorf 926 



Palcemon (Parapalceinon) dolicJiodac/ylus Hilgendori 926 



Pal(ei7ioti (Eupalamon) 7'itse7}icede Man 927 



Palcemon hildehrandti Hilgendorf, and its Varietal Forms 928 



Introduction. 



The collectiou described in this paper was obtained m Mada- 

 gascar in 1911 by the Hon. Paid A. Methuen, to whom I am 

 indebted for the opportunity of examining it. The specimens 

 are the property of the Transvaal Museum, Pretoria, but, by 

 pei-mission of the Acting Director of that institution, a selection 

 from among them, including the holotype of the new species, has 

 been retained for the British Museum. 



For the purpose of comparison with Mr. Methuen 's material 

 the specimens of Potamonidae and Palsemonidse from Madagascar 

 already in the British Museum collection have been re-examined 

 and the results have been incorporated in the paper-. 



The folloAving is a list of the localities whence Mr. Methuen's 

 specimens were obtained. Those from the localities marked with 

 an asterisk were collected for Mr. Methuen by M. Herschell- 

 Chauvin of Tamatave : — 



Eastern Region of Madagascar. 



Manambato, streams running into Lake Rasoabe. July, 



1911. 

 Ambilo, streams running into lagoon. July, 1911. 

 *Rapides de I'lfotiy, a deux joui's de Tamatave. September, 



1911. 

 *Ivondro. August, 1911. 



t Published bv permission of the Trustees of the British Museum. 

 X For explanation of the Plates sec p. 932. 



