244 A. Alcock — Car etiological Fauna of India. [No. 2, 



Mithrax spinifrons, A. Milne-Edwards, Ann. Soc. Ent., France, (4) VII. 1867, 

 p. 263. 



Mithrax affinis, F. de B. Capello, Jorn. Sci., Lisb., 1870-71, p. 264, pi. iii. figs. 

 4, 4a. 



Mithrax (Schizophrys) affinis, triangularis (et varr. excipe var. dichotoma) 

 Kossmann, Beise Both. Meer., Crust., pp. 11 and 13 ; and Schizophrys triangularis 

 var. indiea, Bichters, Mobius, Meeresf. Maurit., p. 143, pi. xv. figs. 8-14. 



Carapace pyriform, its greatest breadth about -^ its length behind 

 the point of bifurcation of the rostral spines, its surface closely and 

 unevenly granular, with scattered sharp tubercles in addition. Exclu- 

 sive of the large unequally-bifid post-ocular spine, the antero-lateral 

 border is armed with six equidistant spines, the last of which is the 

 smallest and is situated on a rather higher level than the others : the 

 posterior border proper is generally beaded, and has its angles pro- 

 duced and upturned. 



The rostrum consists of two stout parallel or incurved spines, the 

 length of which is from one-fifth to one-sixth that of the carapace pro- 

 per, and the outer border of each of which carries a strong accessory 

 spine. 



The basal antennal joint ends in two stout spines, and there is a 

 spine on the sub-hepatic region outside the angle of the buccal frame, 

 and a sharp denticle in the middle of the inferior border of the orbit. 



The chelipeds vary : in both sexes the palm is long — twice the length 

 of the fingers — smooth, polished, and either quite unai'med, or armed, 

 at the near end of the upper border, with a spine or with two or three 

 denticles ; and in both sexes the merus and carpus are either spiny or 

 granular. 



But whereas in old males the chelipeds are stouter than any of 

 other legs, are more than half again as long as the carapace and rostrum 

 and nearly half again as long as the 2nd pair of legs, and have deeply 

 channelled fingers that meet in less than their distal half ; in females 

 and young males they are not stouter than the other legs, are not quite 

 equal in length to the carapace and rostrum or to the second pair of 

 legs, and have the fingers less deeply channelled, and apposable in at 

 least half their extent. 



The ambulatory legs decrease very gradually in length : they have 

 short claw-like dactyli, and the merus is armed at the far end of the 

 upper border with a spine or tubercle. The body and legs are hairy, 

 and the animal frequently protects itself with flat pieces of Nullipore, 

 &c. 



In the collection is a large series of specimens from all parts of the 

 Indian coast, from Mergui and Tavoy on the East to Karachi on the 

 West. 



