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



Leucosia, Bell, Traus. Linn, Soc. Vol. XXI. 1855, p. 281, and Cat. Leucos. Brit. 

 Mns., p. 5. 



Leucosia, A. Milne Edwards, Nouv. Archiv. du Mas. X. 1874, p. 39. 

 Leucosia, Miers, ' Challenger ' Brachyura, p. 322. 



The whole exo-skeleton is of the consistence and appearance of 

 glazed porcelain. 



Carapace extremely convex, sub-circular or subrhomboidal to hexa- 

 gonal in outline, perfectly smooth, with none of the regions — except 

 sometimes the hepatic — defined : in front of the hepatic regions it 

 is produced to form a sort of upturned snout, underneath the tip of 

 which are found the minute eyes sunk in deep round complete orbits, 

 the obliquely-folding antennules, and the minute antennae lying below 

 the antennules. 



The lateral epibranchial angles of the carapace form on either side 

 a distinct lobe, which is bent downwards towards the base of the 

 chelipeds to form the eave of a deep sinuous depression in the side- 

 wall of the carapace, known as the thoracic sinus. 



The true postero-lateral margin of the carapace is ill-defined 

 posteriorly, and the epimeral edge of the carapace — which practically 

 takes the place of most of the postero-lateral margin — is greatly 

 thickened and elegantly milled. These epimeral edges on either side 

 are continuous with a finely-beaded crest that forms the posterior 

 margin of the dorsum of the carapace ; and below this posterior margin 

 the carapace ends in a deflexed posterior wall. 



The buccal cavern is elongate-triangular, and the front part of its 

 side walls are coincident with the sides of the snout-like front of the 

 carapace : the acutely-triangular merus of the external maxillipeds is 

 about as long as the ischium, and the outer margin of the exognath is 

 almost straight. 



The chelipeds are symmetrical and, relatively to the legs, very 

 massive ; they are a little longer in the male than in the female, but are 

 very rarely more than half again as long as the carapace : the margins 

 and certain parts of the surfaces of the arms are ornamented with large 

 polished pearly tubercles : the hands are usually short and broad and 

 little longer than the fingers. The true legs are small. 



The abdomen of the male consists usually of 4 pieces, but the two 

 large middle pieces (which are formed of 5 terga) are sometimes fused, 

 into one : the abdomen of the female also consists of 4 pieces usually, 

 but the large oval third piece (which is formed of 4 terga) is sometimes 

 fused with the second piece. 



The so-called thoracic sinus of Leucosia is simply an invagination of the after 

 part of the pterygostomian region and of the side-wall of the carapace, as may be 

 seen by comparing cleaned carapaces with those of other Leucosines. 



