210 A. Alcock — Carcinological Fauna of foidia. [No. 2, 



carapace and rostrum, the palm being nearly twice the length of the 

 fingers, which are not much arched and meet in their distal half : in 

 the female the chelipeds are rather slenderer than the other legs, and 

 are equal to the postrostral portion of the carapace in length. The 2nd 

 pair of legs are hardly longer than the (male) chelipeds, but are very- 

 much longer than the last three pairs : the dactyli in all are stout, re- 

 curved, and strongly toothed along the posterior margin. 



Specimens are in the Museum collection from Ceylon, Granjam, 

 Mergui, the Nicobars, and the Straits of Malacca. 



Hyastenus diacanthus (de Haan). 



Pisa (Naxia) diacantha, de Haan, Faun. Japon. Crust., p. 96, pi. xxiv. fig. 1. 



Naxia diacantha, Adams and White, ' Samarang ' Crust., p. 10. 



Naxia diacantha, Stimpson, Proc. Acad. Nat. Sci. Philad. 1857, p. 218. 



Naxia diacantha, Heller, ' Novara ' Crust., p. 3. 



Hyastenus diacanthus, A. Milne-Edwards, Nouv. Archiv. du Mus. VIII. 1872, 

 p. 250. 



Naxia diacantha, Brocchi, Ann. Sci. Nat. (6) II. 1875, Art. 2, p. 94, pi. xix. 

 figs. 172, 173 (male appendages). 



Hyastenus diacanthus, Miers, Cat. Crust. New Zealand, p. 9 ; and P. Z. S., 1879, 

 pp. 19 and 26 ; and Zoology H. M. S. ' Alert,' pp. 182 and 194; and ' Challenger ' 

 Brachyura, p. 57. 



Hyastenus diacanthus, Haswell, P. L. S., N. S. Wales, Vol. IV. 1879, p. 442 ; 

 and Cat. Austral. Crust., p. 20. 



Hyastenus diacantlius, de Man, Archiv. fur Naturgesch., LIII. 1887, p. 220. 



Naxia diacantha, C. W. S. Aurivillius, Kongl. Sv. Vet. Akad. Handl. XXIII. 

 1888-89, No. 4, p. 51, pi. ii. fig. 5. 



[Hyast en us diacanthus, Cano, Boll. Soc. Nat. Napol. III. 1889, p. 178.] 



Hyastemis diacanthus, A. O. Walker, Journ. Linn. Soc, Zool., Vol. XX. 1890, 

 p. 109. 



Hyastenus diacanthus, Ortmann, Zool. Jahrb., Syst., etc., VII. 1893, p. 55 ; and 

 Zool. Forsch. Austral. Malay. Archip., Jena., 1894, p. 42. 



Hyastenus diacanthus, Mary Rathbun, Proc. U. S. Nat. Mus. Vol. XVI. 1893, p. 85. 



Body and legs densely tomentose, often much encrusted witb sponges, 

 etc. Carapace pyriform, with the regions strongly convex, well-defined, 

 and when denuded, smooth and polished : on the gastric region, in the 

 middle line, there is an acuminate tubercle, on either pterygostomian 

 region at least oue large tooth, and near the hinder limit of either 

 branchial region a horizontally projecting lateral epibranchial spine. 



The rostrum consists of two more or less divergent horns, the 

 length of which in the adult male is from half to nearly two-thirds 

 that of the carapace proper, but in the female is less. The basal 

 antenna! joint is much inflated behind and constricted in front. 



