1899.] A. Alcock — Carcinological Fauna of India. 19 



in the middle line, its breadth (exclusive of the inner supra-orbital 

 angles) is from half to a third the greatest width of the carapace. 



Antero-lateral borders little oblique, moderately arched, cut into 

 five lobes or teeth, including the outer orbital angle. 



Basal antenna-joint short but not peculiarly broad, its outer angle 

 is produced as a lobule that meets tne front and fills the orbital 

 hiatus so as to exclude the flagellum. 



The two fissures in the upper edge of the orbit may be distinct, or 

 may be almost indistinguishable. The antennules fold nearly trans- 

 versely or a little obliquely. 



Epistome short, and though well enough demarcated from the 

 palate, somewhat overlapped by the external maxillipeds. Buccal 

 cavern squarish, broader than long, the efferent branchial channels 

 well defined. 



Chelipeds short, but a little longer than the legs : arm short, 

 without any distinct spines, only the inner angle of wrist dentiform ; 

 palm not prismatic, fingers stout and rather shorter than the palm. 



The propodite and dactylus of the last pair of legs are typically 

 foliaceous swimming paddles, but the carpus and merus are not parti- 

 cularly dilated. 



The abdomen of the male consists of 5 pieces, the 3rd-5th terga 

 being fused. 



Lissocarcinus is distinguished from Thalamonyx chiefly by the sub- 

 circular or obovate carapace and by the stumpy little sculptured 

 chelipeds. 



Key to the Indian species of Lissocarcinus. 



I. Carapace as long as broad, flat, obovate ; front broadly trian- 

 gular, notched at tip ... L. polybioides. 



II. Carapace broader than long, convex : — 



1. Carapace sub-rotund ; front sub-entire, being dorsally 

 grooved but not notched in the middle line, supra- 

 orbital angles obscurely defined L. orbicularis. 



2. Carapace distinctly broader than long ; front cut 



into two broad lobes exclusive of the well defined 

 dentiform supra-orbital angles ... L» lasvis. 



4. Lissocarcinus polybioides, Adams and White. 



Lissocarcinus polybioides^ Adams and White, Samarang Crust, p. 46, pi. xi. fig. 

 5 t A. Milne Edwards, Archiv. du Mus. X. 1861, p. 417 : Haswell, Cat. Austral. Crust. 

 p. 83 : Miera, Challenger Brachyura, p. 205 : J. R. Henderson, Trans. L^n. Soc. 

 Zool., (2) V. 1893, p. 378. 



