1899.] A. Alcock — Carcinological Fauna of India. 73 



the pi'ocess bein^ in close contact with the whole length of the inner 

 supra-orbital angle and completely filling the orbital hiatus, from which, 

 therefore, the antennal flagellum is widely excluded. 



Epistome sufficiently long : buccal cavern squarish, broader than 

 long, the efferent branchial channels well defined. 



Chelipeds and legs as in Charybdis {=-Goniosoma), Abdomen as in 

 Neptunus. 



Obviously different as the extremes are, the forms included under 

 Charybdis ( = Goniosoma) and Thalamita yet constitute an unbroken 

 series, and there is no one character, still less a combination of charac- 

 ters, by which the two groups can be sharply segregated. 



Among Indian forms, however, even the most Charybdis-like 

 Thalamites (e.g. T. exetastica and impariviamis) never have more than 

 five distinct teeth on the antero-lateral border (though T. exetastica has 

 a microscope accessory (6th) denticle on the first tooth), and always 

 have a characteristic broadening of the inner supra-orbital angle ; while 

 the most Thalamita-like Charybdes (e.g. C. investigatoris) has the antero- 

 lateral border cut into six distinct teeth and has a narrow inner supra- 

 orbital angle. 



Key to the Indian species of the genus Thalamita. 



The extreme extent of the basal antenna-joint is far 

 greater than the major diameter of the orbit : — 



A, Front cut into six lobes of nearly equal size — 



exclusive of the broad inner Bupra-orbital 



angles : — 



1. Antero-lateral borders of carapace cut 

 into five teeth of nearly equal size : — 



i. Transverse ridges of carapace 

 faint : outer surface of palms nearly 



smooth T. crenata, 



ii. Transverse ridges of carapace very 

 distinct : outer surface of palms 

 costate T. danx. 



2. Antero-lateral borders cut into five teeth, 

 of which the 4th is much the smallest: — 



■ i. Fourth tooth rudimentary : crest of 

 basal antenna- joint with some large 



spines T.prymna. 



ii. Fourth tooth rudimentary : crest of 



basal antenua-joiut smooth T. picta. 



iii. Fourth tooth small : basal antenna- 

 joint granular , , , T. stiwpsoai, 



J. II. 10 



