1896.] A. Alcock — Carcinological Fauna of India. 221 



50. Leucosia marmorea, Bell. 



Leucosia marmorea, Bell, Trans. Linn. 9oc. Vol. XXI. 1855, p. 286, pi. xxx. 

 fig. 4: E. Nanok, Zeits. Wiss. Zool. XXXIV. 1880, p. 49 {gastric teeth): A. O. 

 Walker, Journ. Linn. Soc, Zool., Vol. XX. 1890, p. 111. 



Carapace highly polished, piriform, longer than broad by the whole 

 extent of the front : its antero-lateral borders finely beaded, slightly 

 sinuous, and gradually convergent : its true postero-lateral border bead- 

 ed only as far as the level of the first pair of legs (2nd pereiopods) : 

 its epiraeral edge not visible in a dorsal view : its finely-beaded 

 posterior margin almost straight, with the surface below it quite smooth. 



The thoracic sinus is a roughly Y-shaped cavity, the tail of the Y 

 being defined by a line of 5 or 6 small pearly granules continuous with 

 the milled epimeral edge, the concavity of the Y being defined by the 

 convex, very finely crenulated edge of the pterygostomian region, and 

 both limbs of the Y being very short. 



The hepatic regions are hardly defined posteriorly by a faint crease, 



The front is prominent, dorsally convex, and truncate-triangular, 

 ending in three minute teeth, of which the middle one is the largest. 



The ventral surface of the ischium of the external maxillipeds of 

 the female is smooth, and not strongly convex. 



Chelipeds little longer than the carapace. The arm has its three 

 borders tuberculate ; its upper surface with 5 to 7 pearly tubercles, in 

 two short rows, in its basal half, just beyond a basal eminence formed 

 of 6 to 8 coalescent granules ; its inner surface granular or tubercular 

 in rather more than its basal half, and its under surface in rather more 

 than its basal third. The wrist and hand both have a row of sharp- 

 cut granules along their inner edge. Ths fingers, which meet only at 

 their tips, have the opposed edges distantly crenulate. 



The legs are slender : their meropodites are subcylindrical with 

 longitudinal rows of microscopic granulation, dorsally and ventrally ; 

 their propodites have sharpish edges, but are not dilated : their dactyli, 

 which are somewhat longer than the propodites, are very narrowly 

 lanceolate. 



Colours in spirit : rich warm yellowish-brown with two pale round 

 spots on either side of the gastric region. 



Length of carapace of an adult female 23 millim., breadth 18'5 

 millim. 



A young and four adult females from the Andamans. 



Among Indian species of the L. longifrons group, this is at once 

 recognized by its elongate piriform carapace, by its truncate front, by 

 its nearly straight posterior margin, by its slender legs, and by its 

 warm cinnamon brown colour. 



