TO INDIAN CARCINOLOGT. 415 



The total length of an adult is about 55 ram. 



There is considerable variation in this species as regards the amount of granulation on 

 the larger chela ; indeed, I have met uith a few specimens in which the granules are 

 almost subspiniform. The marginal teetli of the carpus, hand, and finger are much more 

 pj'ominent in some individuals than in others, but are never absent ; the form of the hand 

 also varies slightly. I met with a specimen in wliich the left chela had the characters 

 of a fully-developed right chela; it had jjrobably been repaired, but in any case illustrated 

 a reversion to the primitive state of equal and similar chelipedes. De Man has recently 

 described an allied species D. iiitermedlus, from Celebes (Max Weber's Crust, p. 352), 

 which is apparently distinguished among otlier characters by its more deeply cleft an- 

 tennal acicle, the inner fork of wliich extends beyond the middle of the penultimate 

 peduncular joint, and by the granules on the outer surface of the larger chela being less 

 numerous, but sharp and subspiniform. 



Distrlbutiou. Indian Seas {Fahricius, 2Iilue-Edii:unh) ; Mergui {Be Man). 



211. Diogenes affinis, n. sp. (PI. XXXIX. figs. 1, 2.) 



D. custus, Dana, Crust. U.S. Explor. Expcd. pt. i. p. 439, pi. xxvii. tig. 10 (i<S52j ; Hcndei'sou, 

 'Challenger' Anomura, p. 53 (1888), ncc D. custos, Fabr. 



Madras, eight specimens ; not common (J. E. H.). 



This species is closely allied to D.cuslos, but distinguished as follows : — The ophthalmic 

 process is short, and broad especially towards its distal end, extending only to the ends of the 

 ophthalmic scales, or very slightly beyond these, with the lateral spinules almost obsolete, 

 but the terminal ones well developed and in line with the spinules of the scales. The eye- 

 stalks, antennal and autennular peduncles, are relatively shorter and stouter than in 

 jD. castas ; the antennal flagellum is stout and not twice the length of the peduncle, with 

 long fringing hairs, whereas in D. ciiatos it is considerably longer. The antennal acicle does 

 not reach the end of the penultimate peduncular joint, and is scarcely produced intern- 

 ally at its base, certainly not bifurcate as in I), custos. The antcnnular peduncles are 

 barely as long as the antennal peduncles, whereas in J), custos they are slightly longer. 



The hand of the left chelipede is shorter and broader, also more compressed and the 

 finscrs more abbreviated than in J), custos, w hile the lower margin of the immobile 

 finger is thin and slightly sinuous. 1\\ other respects the two species closely agree. 



The largest specimen is 35 mm. long, and a female with ova is only 20 mm. in total 

 length. 



All my specimens share the above characters and do not vary to any great extent from 

 each other. I have compared thctn with a large series of D. custos of similar size, from 

 Madras. The species may be recognized at once by the characters of the ophthalmic 

 process, but as a general shortening seems to have taken place in connection with the 

 eye-stalks, antennal and antennular peduncles, it may possibly come to be regarded as 

 merely a variety of D. custos ; I do not, however, think this probable, and in any case 

 it is worthy of a distinctive name. There can be no doubt that it is the species figured 

 by Dana as D. custos ; I have re-examined the Australian specimen which I referred to 

 D. custos, in the Eeport on the ' Challenger' Anomura, and I lind it identical with the 



59* 



