58 A. Alcock — Carcinological Fauna of India. [No. 1, 



The clielipeds are about 2i times the length of the carapace (in the 

 adult male), and when denuded are smooth and polished except for cosfsa 

 on the wrist and hand, and for granules on the far end of the npper sur- 

 face of the arm. There are only two enlarged spines on the anterior 

 border of the arm, and the posterior border of the arm is, spineless. Wrist 

 with granular costse on the upper and outer surface, with the inner 

 angle strongly spiniform, and with three spinules at the outer angle. 

 Palm inflated, barrel-shaped, 6-costate, the four upper costae granular ; 

 only three spines — and those small — on the upper surface. Fingers of 

 the larger cheliped a good deal shorter than the palm. 



Merus of last pair of legs f to f as broad as long, with a spine, as 

 usual, near the far end of the posterior border : the same border of the 

 propodite is smooth. 



The 2nd and 3rd abdominal terga in both sexes — as well as, to a 

 less extent, the 4th in the female — are transversely carinate : the 6th 

 tergum in the male is transversely oblong with the anterior (true 

 posterior) angles rounded. 



In the Indian Museum are 66 specimens, chiefly from the Madras 

 and Orissa coasts, but also from Bombay and Karachi. 



The carapace of an exceptionally large male is 29 millim. long and 

 46 millim. in extreme breadth. 



This species is easily distinguished from 0. variegafa De Haan, 

 with which it appears to have been confounded, by the following 

 characters : — 



(1) the carapace is very decidedly convex in its posterior half, the 

 regions are less clearly defined, and there is only one transverse ridge 

 on the epibranchial regions — namely the usual one that runs in from 

 the last antero-lateral tooth : 



(2) the four middle frontal teeth are blunter and more divergent, 

 and the third on either side is larger and more prominent : 



(3) the edges of the teeth of the antero-lateral border are serrulate : 



(4) the eyes are smaller and the orbits have a much less marked 

 dorsal inclination ; the little lobule at the outer end of the lower border 

 of the orbit is obsolete, instead of being a sharp independent denticle, 



(5) there is a ridge, but no tooth, on the lobe of the basal antenna- 

 joint. 



(6) there are only 2 large spines on the anterior border of the arm, 

 there are no squamiform granules on the under surface of the arm and 

 hand, there are three spinules on the outer surface of the wrist ; the 

 palms are more inflated, their costae less numerous and less salient, and 

 both the spines immediately behind the finger-joint are obsolete : 



(7) the sixth abdominal tergum of the male is transverse oblong 

 with the anterior angles rounded off. 



