210 
A. Alcock — Carcinological Fauna of India. 
[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, Ganjam, 
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 diacanthus, 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. 
\Hyastenus diacanthus, Cano, Boll. Soc. Nat. Napol. III. 1889, p. 178.] 
Hyastenus 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 with 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 one 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 
antennal joint is much inflated behind and constricted in front. 
