II. SYSTEMATIC PART 



Group BRACHYURA 



Section Cyclometopa 

 Family POTAMONID^ 



Thelphmixiens, Milne Edwards, Hist. Nat. Crust., II., p. 7, 1837. 



Telphusinea vel Cancroidea Grapsidica, Dana, U.S. Expl. Exp., Crust., Pt. I., p. 292, 1852. 



rhelplnisinw, Milne Edwards, Ann. Sci. Nat. Zool. (3), XX., 18.53, p. 207. 



Telphusidw, Wood-Mason, Journ. Asiatic Soc, Bengal, XL., pt. ii., 1871, p. 192. 



Potamonidm, Ortraann, Zool. Jahrb., Syst., IX., 1896, p. 445, and X., 1897, p. 296. 



PoTAMONiD.T-, Maby J. Rathbun, Nouv. Archiv. du Muskum (4), VI., 1904, pp. 244, 245 (h6/ lit.). 



Carapace variable in shape — subquadrilateral, or oval, or even subcirciilar, 

 but commonly broader than long ; its regions may be either well or quite ill 

 defined, but are seldom areolated to any marked extent. " Cervical groove " 

 commonly clear and deep in all its extent ; but sometimes interrupted, and not 

 unseldom well defined only behind the mesogastric area. 



Front in the adult almost always broad, only exceptionally as narrow as, 

 or narrower than, the orbit ; not separated from the inner supra-orbital angles ; 

 generally more or less deflexed, but occasionally hardly declivous at all ; as a 

 rule, broadly — even obscurely- — bilobed, seldom (never in any Indian species) 

 spinose. 



Antero-lateral borders of carapace usually well arched and not longer 

 (even sometimes shorter) than the postero-lateral borders, which are 

 convergent. 



Epistome well defined, of good length fore and aft, not encroached upon 

 by the external maxillipeds. 



Sternum broad. Abdomen of the male covering all the space between the 

 last pair of legs. Genital ducts of the male opening free on the coxopodites of 

 the last pair of legs. 



The antennules usually fold transversely in narrow fossae. 



Antennal peduncles usually occupying the orbital gap, the distal joints 

 usually overlapped l)y the front. Antennal flagella short, sometimes quite 

 vestigial. 



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