198 A. Alcock — Garcinological Fauna of India. [No. 2, 



Mensethius monoceros, Mier3, Phil. Trans. Vol. 168, 1879, p. 485, and Zoology 

 'Alert,' pp.. 182, 190, 517 and 521, and 'Challenger' Brachyura, p. 37. 



Mensethius monoceros, Haswell, P. L. S., N. S. Wales, Vol. IV. 1879, p. 437, and 

 Cat. Austr. Crust., p. 9. 



Mensethius monoceros, de Man, Notes Leyden Mus. II. 1880, p. 171, and Archiv. 

 f. Naturges. LIII. 1887, i. 219. 



Mensethius monoceros, Richters in Mobius Meeresf. Mauritius, p. 145. 



[Mensethius monoceros, Cano. Boll. Soc. Nat. Nnpol. III. 1889, p. 175.] 



Menasthius monoceros, Henderson, Trans. Linn. Soc. Zool. (2) V. 1893, p. 342. 



Mensethius monoceros, Ortnaann, Zool. Jahrb. Syst., etc., VII. 1893, p. 41. 



Carapace elongate-triangular, most markedly so in the male, the 

 lateral epibranchial angles sharp-cut, and the surface very variably 

 tuberculated. 



The rostrum, which is flanked on either side by the forwardly- 

 directed supra-ocular spine, is styliform, acute, and horizontally com- 

 pressed, its length being about half that of the carapace in the male, 

 but a good deal less in the female. 



The small eyes are imperfectly retractile, and project freely from 

 beneath the supra-ocular spine. 



The chelipeds in the male are ag long as, or a little longer than, the 

 2nd pair of legs, or about equal in length to the carapace and rostrum : 

 they are very much stouter than any of the other legs, and have a 

 somewhat inflated palm, and fingers which meet only at the tips. 



The chelipeds in the female are not stouter than the other legs, and 

 are considerably shorter than the next pair of legs, which, again, are a 

 good deal shorter than the carapace and rostrum : the fingers meet 

 through the greater part of their extent. 



The 3rd-5th pair of legs are very much shorter than the 2nd 

 pair : in all the dactyli are strongly recurved and are toothed along 

 the posterior margin. 



Very numerous specimens from the Andamans and Nicobars. 



Acanthontx, Latr. 



[Acanthonyx, Latreille, Regne Animal, (2) IV. 58.] 

 Acanthonyx, Milne- Edwards, Hist. Nat. Crust. I. 342. 

 Acanthonyx, A. Milne-Edwards, Miss. Sci. Mex., Crust. I. 142. 

 Acanthonyx, Miers, Journ. Linn. Soc, Zool., Vol. XIV. 1879, p. 650; and ' Chal- 

 lenger' Brachyura, p. 42. 



Carapace sub-oblong, rounded behind, and with the dorsal surface 

 usually depressed, not markedly constricted behind the prominent antero- 

 lateral angles, the lateral branchial spines small and not prominent. 

 Prte-ocular spine prominent, acute. Spines of the rostrum united at 

 the base, acute and but little divergent. Post-abdomen in the male six- 

 jointed. Eyes small, mobile, but not completely retractile. Basal an- 



