430 Oarcinological Fauna of India. 



This species differs from 0. halansse in tlie following^ particulars : — 



(1) the carapace is decidedly broader tlian long, its lobulations are 

 not nearly so bold and convex, and the outer post-frontal lobules may 

 be entire : 



(2) the free edge of the front is not turned up to form a trenchant 

 horizontal crest, although it is well defined : 



(3) the cVielipeds of the male are far more massive than any of the 

 legs; the inner border of the arm is dilated distally ; the palm is a good 

 deal swollen, the pectinate ci-est that traverses its vipper surface is 

 longer, and its inner surface is more granular ; the fingers are more 

 widely separated when closed, and the lamellar tubercles along the 

 upper border of the dactylus are more numerous : 



(4) it is a smaller species. 



In the Indian Museum are 10 specimens from the ^icobars : the 

 carapace of the largest egg-laden female is 10 millim. long and 12 

 broad. 



Metaplax, Edw. 



Metaplax, Milne Edwards, Ann. Soi. Nat. Zool. (3) XVIII. 1852, p. 161. 

 Rhaconotus, Gerstaecker, Archiv f. Naturges. XXII. 1856, i. p. 140, and 

 Kingsley, Proo. Ac. Nat. Sci. Philad., 1880, p. 213. 



Metaplax, de Man, Jom-n. Linn. Soo., Zool., XXII. 1888, pp. 158-155. 



Carapace quadrilateral, somewhat depressed, a good deal broader 

 than long, the regions well or fairly defined and the cervical and 

 branchial grooves distinct. 



Front declivous, its breadth about a third or a fourth that of the 

 carapace, the convexity of its free edge impinges on the epistome to 

 help in forming the broad interantennulary septum. 



Lateral borders of the carapace straight, or a little arched anteriorly, 

 nearly parallel, cut into 4 or 5 teeth of which the last one or two are 

 very inconspicuous. The posterior part of the sidewalls of the 

 carapace with some hairs curving towards the incurrent branchial 

 opening. 



Orbits of good depth : their outer wall incomplete, their lower 

 border crenulate : the eyes do not fill the orbits and the eyestalks are 

 not prolonged. 



The autennules fold nearly transversely : the septum between 

 them is broad. The antennjB lie in the orbital hiatus, their basal joint 

 ia extremely short, their flagellum is of fair length. 



Epistome short, but well defined and prominent : buccal cavern 

 squarish : the external maxillipeds leave between thein a large rhomb- 



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