PARREYSTA. 159 



The antei'ior and posterior cicatrices are distinct, tlie apical 

 ones disposed on the underside of the cardinal tootli. 



Taken by the author of tlie species at Uhitoura, between Cawn- 

 pore and Allahabad and represented by specimens in the Indian 

 Museum Collection from the following localities : — Moradabad ; 

 Eiver Indus; Barrack Eiver; ISilcher; Kajputana; Berhampur ; 

 Dacca ; E. Cachar ; Sylhet ; Tezpore ;. Poona ; Karnul, Madras ; 

 Calcutta {J. Wood-Mason); Arrali ; liajraahal; Hazrapur ; Eani- 

 gunga ; Bunderbunds. 



An enormously variable species, of which many varieties have 

 been described, several of these appear, however, to be somewhat 

 obscure; the original descriptions are nevertheless given below: — 



Yar. marcens {Benson), A. M. N. H. x, 1862, p. 188. 

 Unio marcais, H. & T., C. I. 1876, p. 19, pi. 42, figs. 1-6. 



Original description : — Banded with olive and green ; nacre 

 salmon-coloured ; beaks nearly smooth, eroded ; sulci obsolete ; 

 lunule narrow. 



Long. 44, lat. 06, diam. 27 mm. 



Hah. Berhampooter Eiver, Assam. 



Var. trigona {Benson). 



Unio favidens, var. densa, A. M. X. II. x, 1802, p. 188. 



Original description : — Shell with a piceous epidermis, more 

 oblique ; beaks and nacre as in type ; lunule broad. It shows an 

 inclination to verge towards U. triemholus. 



Long. 44, lat. 67, diam. 27 mm. 



Hab. Nujeebabad, in the North-west of Eohilkund. 



Var. densa {Benson). 



Unio favidens, var. densa, A. M. N. H, x, 1862, p. 189. 



Original description : — More solid and tumid [than the typical 

 form] ; epidermis yellow-brown, eroded ; lunule as in type ; shell 

 more oblique. 



Long. 33, lat. 47, diam. 24 mm. 



Hah. Ganges Eiver, above Chumir, between Allahabad and 

 Benares. 



Var. deltae {Benson). 



Unio favidens, var. deltes, A. M. N.H. x, 1862, p. 189; II. & T., 

 C. I. 1870, p. 19, pi. 42, fig. 2. 



Original description : — Epidermis olive-green and yellow, rayed; 

 nacre salmon-coloured ; ruga) on umbones very distinct, some also 

 on the upper part of the umbonal hinder slope ; luuule somewhat 

 broader than in the type ; cardinal teeth narrower. 



Long. 34, lat. 47, diam. 24 mm. 



