1S96.] A. Alcock — Carcinological Fauna of India. 223 



Leucosia obscura, Bell, Trans. Linn. Soc. Vol. XXI. 1855, p. 285, pi. xxx. fig. 3, 

 and Cat. Leucos. Brit. Mas. p. 7. 



Leucosia pallida, var. obscura, Miers, Ann. Mag. Nat. Hist. (5) V. 1880, p. 316. 

 ? Leucosia parvimana, Stimpson, Proc. Ac. Nat. Sci. Philad. 1858, p. 159. 

 ? Leucosia moresbiensis, Haswell, P. L. S., N. S. Wales, Vol. IV. 1879, p. 49. 

 ? Leucosia perlata, de Man, Notes Leyden Mus. III. 1881, p. 124 : Ortmann, Zool. 

 Jahrbiich. Syst. etc., VI. 1892, p. 584. 



Carapace more nearly circular than in any other species of the 

 genus, owing to the convexity of the antero-lateral margins ; its surface 

 perfectly smooth ; its antero-lateral margins crenulate : ifcs true postero- 

 lateral margins beaded almost up to the level of the 2nd pair of legs 

 (3rd pereiopods) ; its epimeral edge not visible in a dorsal view ; its 

 posterior margin in the adult, as well as in the young, nearly straight, 

 salient, and having the outer angles dentiform, the deflexed surface below 

 being quite smooth. 



The thoracic sinus is a Y-shaped cavity of no great depth ; the tail 

 of the T being defined by a row of 6 or 7 granules, three or four of which 

 are large and pearl-like ; the concavity of the fork of the Y being defined 

 by the convex smooth edge of the pterygostomian region ; and both 

 limbs of the Y being equally short. 



The front is much broader than long and is distinctly con,cave in the 

 mid-dorsal line, anteriorly ; it ends in three denticles, the middle one of 

 which is the most prominent. 



The ventral surface of the ischium of the external maxillipeds of 

 the female is strongly convex up to a stout terminal tooth. 



The upper surface of the arm is traversed, in its proximal half, by 

 7 to 9 pearly tubercles arranged in two rows running forwards from the 

 basal eminence formed by the usual mass of coalescent granules : the 

 inner edge of the upper surface of the wrist bears a few tiny tubercles : 

 the hand, which is more than three-fourths as broad as long, has its outer 

 edge strongly carinate, and its inner edge granular : the fingers meet 

 only at their tips, where alone they are faintly denticulate, their length 

 is four-fifths that of the hand. 



Except that they are more slender, and have sharply carinated 

 propodites, and slender very narrow dactyli, the legs are as in 

 L. longifrons. 



Colours in spirit : delicate lavender grey marbled with darker ; a 

 pair of brown spots in the posterior part of the carapace, and two pairs 

 of pale spots in the gastric region. 



The carapace of an adult female is 21 millim. long and 18 millim. 

 broad. 



In the Indian Museum collection are 3 adult females (one with eggs) 

 from the Andamans, and a young male from the Persian Gulf. 



