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



The Indian species of the genus Neptunus fall into five groups, or 

 subgenera, which are characterized as follows : — 



I. Carapace very broad, little convex, and having the jnnc- 

 tion of the posterior with the postero-lateral angles 

 rounded. Front not projecting beyond, or even reced- 

 ing behind, the internal supra-orbital angles : the last 

 spine of the antero-lateral borders enormously larger 

 than any of the others. Orbits of moderate size and 

 having only a slight dorsal inclination. Antero-exter- 

 nal angle of basal antenna- joint produced toa spiniform 

 process lying in the orbit. Epistome produced in the 

 middle line to form a very prominent spine : the antero- 

 external angle of the merus of the external maxillipeds 

 rounded, not produced laterally. Hand at least as mas- 

 sive as the arm Neptunfs. 



II, Carapace moderately broad, little convex, and having 

 the postero-lateral junctions rounded. Front hardly 

 projecting beyond the internal supra-orbital angles, but 

 not receding : the last spine of the antero-lateral borders 

 a good deal the largest. Orbits large, with a very 

 strong dorsal inclination. Antero-external angle of 

 basal antenna-joint forming a blunt lobe-like process. 

 Epistome slightly produced in a spiniform manner : the 

 antero-external angle of the merus of ths external 

 maxillipeds strongly produced in a lateral direction. 

 Hand at least as massive as arm Amphitrite. 



III, Carapace suborbicnlar or not very broad, flat, the 

 postero-lateral junctions rounded. Front slightly projec- 

 ting beyond the internal supra-orbital angles : the last 

 spine of the antero-lateral border either hardly larger or 

 actually smaller than any of the others. Orbits of 

 moderate size and with a moderate dorsal inclination. 

 Antero-external angle of basal antenna-joint forming a 

 lobe-like process. Epistome hardly produced in the 

 middle line : antero-external angle of merus of external 

 maxillipeds strongly produced in a lateral direction. 



Hand hardly less massive than the arm Achelous. 



IV. Carapace moderately broad, flat or little convex, and 

 having the postero-lateral junctions angular or actually 

 spiniform. Front decidedly prominent beyond the 

 inner supra-orbital angles : the last spine of the antero- 

 lateral borders very much the largest. No free pro- 

 longation of the epistome in the middle line. Hand 

 about as massive as arm. [Except in N. spinipes, the 

 angle of the basal antenna-joint is a lobe-like process. 

 Except in N. tuherculosus and hrochii, the orbits are 

 large with a very strong dorsal inclination. Except 

 in N. hastatoides, the antero-external angle of the 



