418 Ml?. J. R. HENDERSON — A CONTRIBUTION 



The largest specimen I have examined is only 20 mm. in length ; Heller's type was 



22 mm. long. 



The specimen from Singapore, figured by Walker as perhaps a variety of D. avanis, 

 is not, I think, referable to this species. 



JDlstrihiition . Bay of Bengal — Nicobars {Heller) ; Mergui {Dc Man). 



215. Diogenes costatus, n. sp. (PI. XXXIX. figs. 7, 8.) 



Rameswaram, one specimen; Tuticoriu, one specimen {Tlmrston); Madras, not 

 common, twelve specimens {J. R. H.). 



The ophthalmic process is very narrow and entire, not reaching the aj)ices of the 

 ojihthalmic scales. The ophthalmic scales are subtriangulate, with merely two or three 

 spinules towards the apes. The antennal acicle is straight, scarcely reaching the distal 

 end of the penultimate peduncular joint, with no trace of bifurcation, and with from 

 six to eight well-marked spinules on the inner margin. The eye-stalks scarcely reach 

 the middle of the last antennal peduncular joint. The antennular peduncles are longer 

 than the antennal peduncles by nearly half the length of their last (antennular) joint. 

 The antero-lateral margin of the carapace is armed with about seven spinules. 



The left chelipede has the merus dentate along its inferior margin. The carpus is 

 granulated externally, and the upper margin carries about twelve short teeth, of which 

 the distal one is larger than any of the others ; the antero-esternal margin, bounding the 

 carpo-propodal articulation, carries about sis small teeth, and a few are also seen on the 

 lower distal margin. The hand is almost smooth esternally, but has a prominent, 

 though short, oblique granulated ridge, commencing at the proximal inferior angle and 

 passing for some distance parallel to the carpal articulation ; the upper margin is pro- 

 vided with subsj)iniform granules, and a few more sliglitly marked granules are seen on 

 the lower margin, which is faintly concave, i. e. the immobile finger is not in the 

 same straight line, but is somewhat deflexed. The upper margin of the mobile finger 

 is finely crenated. The ambulatory legs are almost smooth, with the anterior margins 

 pubescent and very faintly toothed. 



Length of body 18 mm., of left chelipede 20 mm., of carpus 5"5 mm. ; the propodus is 

 8'8 mm. long and 4-8 mm. in height, the dactylus 5-8 mm. long, and the second ambu- 

 latory leg 21 mm. long. 



This species is distinguished by the ridge on the proximal outer surfjxee of the hand. 

 It is separated from D. avarus, which has a faint longitudinal ridge, by the very different 

 form of the left chelipede, and by other characters. A trace of the hand ridge is also 

 seen in the Atlantic D. varlans (Costa), but although this species agrees in some respects 

 with ours, the form of the left chelipede, the armature of the carpus, and the proportions 

 of this joint are quite different in tlie two species. D. graniilatiis, Miers (from West 

 Austi'alia), judging from the type, which is dried and not in very good order, is an allied 

 species, but in it the ophthalmic scales are entire, the antero-lateral margin of the 

 carapace is unarmed, the carpus is less strongly toothed, and has no antero-exterual 

 spinules, Avhile the baud is uniformlj^ granulated esternallj^, and has only a very slight 

 carina. 



