1896.] 



A. Alcock — Carcinological Fauna of India. 



157 



" bicarinate," or compressed and unicarinate, and (2) the extent of the 

 raised posterolateral border — whether stopping short of the great 

 lateral spine, or prolonged into the border of that spine. With regard 

 to the first of these characters, it may be remarked that the distinction 

 drawn is between a distinctly compressed carpus, and a distinctly in- 

 flated carpus. With regard to the second, the distinction drawn is 

 between a sharply-raised border that (in any position of the carapace 

 and in any light) can be plainly seen to form a considerable part of the 

 hinder border of the great lateral spine, and a boi'der that stops at the 

 base of the spine or even farther- behind. The sculpture of the lower 

 part of the outer surface of the hand is also very definite in all the 

 species, and — if age and .sex be taken into due consideration — the 

 sculpture of the median ridge of the hand and of the dactylus. The 

 presence or absence of a tubercle on the postero-lateral border is also 

 of importance. 



Key to the species of Matuta. 



[I. Carapace pentagonal, lateral epibranchial spine 



rudimentary ... ... ... M. inermis.* ] 



II. Carapace more subcircnlar than pentagonal, 

 lateral epibranchial spine greatly developed 

 (Indian species) : — 



1. Front just equal to the orbit in width, 

 rostrum simple or faintly emarginate : 

 a sharply defined acute tubercle near 



the middle of the posterolateral border M. banksii. 



2. Front distinctly wider than the orbit, 

 rostrum distinctly bilobed : postero- 

 lateral border with or without an 

 obscurely defined eminence near its 

 middle : — 



i. Postero-lateral border elevated 

 throughout, forming a con- 

 siderable part of the hinder 

 border of the great lateral 

 spine, and without any trace 

 of a tubercle or eminence : 

 lower surface of hand very 

 rough in the adults of both 

 sexes ... ... M. miersii, 



* M. inermis, Miers, Zoology H. M. S. 'Alert,' p. 256, pi. xxvi, fig. G. Known 

 only from the Melanesian part of the Indo- Pacific area. 



