Carcinological Fauna of India. 169 



The chelipeds, though actually slender, are relatively to the cara- 

 pace as stout and long as those of the longer-armed species of Lambrus : 

 they are one-third longer than the combined carapace neck and rostrum : 

 they are sub-cylindrical and spiny : their proportions are much those 

 of Lambrus, the fingers being not much more than a quarter the length 

 of the palm. The fingers are curved, and are in contact only at their tips. 



The legs, which are very slender and are not quite so long as the 

 chelipeds, display no remarkable characters. 



The figure, which represents a male magnified two diameters, shows 

 the proportions better than any table of measurements. 



Loc. Port Blair, Andaman Islands. 



Achjius, Leach. 



Achseus, Leach, Malac. Podophth. Brit., Tab. XXII. fig. C. 

 Achseus, Desmarest, Consid. Gen. Crust., p. 153. 

 Achseus, Milne- Edwards, Hist. Nat. Crust. I. 281. 



Achseus, Miers, Journ. Linn. Soc, Zool., Yol. XIV. 1879, p. 643; and 'Challenger' 

 Brachyura, p. 8. 



Carapace triangular with the branchial regions swollen, always 

 more or less constricted behind the eyes. Rostrum very short, bifid. 

 Eye-stalks long and hardly retractile backwards : no orbits or post-ocular 

 spine. Antennae with the basal joint very slender, sub-cylindrical, the 

 other joints and the nagellum completely exposed. External maxillipeds 

 with the meropodite long, narrower than the ischiopodite, and carrying 

 the next joint at, or near, its apex. Chelipeds short, not very stout. 

 Legs slender, sometimes long and filiform : the dactyli of those of the 

 last two pairs more or less falcate. Abdomen consisting of six segments 

 in both sexes. 



As Miers has remarked, this genus is distinguished from Steno- 

 rhynchus only by the form of the rostrum, which consists of two short 

 lobes instead of two long spines. 



Key to the Indian species of the genus Achseus. 



I. Carapace with a post-ocular constriction, but with no 

 long post-ocular " neck : " dactyli of last pair, or two 

 pair, of legs strongly falciform : — 



1. Carapace and eye-stalks smooth ... A. lacertosus. 



2. Carapace with a bilobed prominence on the cardiac 



region : eye-stalks with a tubercle on the an- 

 terior surface : — 



i. Gastric region smooth .;. ... A. affinis. 



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