I9I9-] N. ANNANDAr.E& B. Prashad : Gangetic Delta Molluscs. 243 



Dostia depressa (Benson). 

 (Plate XX, fig. 2b). 



1836. Benson, of), cit., p. 748. 

 1868. Blanford, op. cit.. p 60. 



1915. Septaria crepiditlaria and .S". depressa, Preston, Rec. hid. Mns., XI, 

 p. 480. 



The shell of this species differs from that of D. cornucopia in 

 being as a rule narrower in proportion to its length, in having the 

 true mouth still smaller, in the smoother edge of the columellar 

 septum and in colour. The shell substance is rather thicker and 

 has a yellowish tinge. The columellar plate and the outer lip are 

 tinged more or less deeply with orange or coral-red, but this tint is 

 somewhat evanescent. The periostracum is brownish, sometimes 



a. 



Text-fig. i. — Radular teeth of Gangetic species of Dostia. 

 [a) D. depressa, Benson. (b) D. platyconcdia, sp. nov. 



with transverse greenish lines, an:l occasionally marbled with green. 

 When the periostracum is worn away, the surface of the shell is 

 whitish with transverse zig-zag pink or purple lines and stripes. 

 The operculum differs from that of D. cornucopia in bsing rela- 

 tively broader, in having the lateral process longer and more 

 pointed, and in other characters shown in our figure. 



We have seen this species from the deltas of the Ganges 

 and the Irrawady, where it is usually found in slightly brackish 

 water. It is common on the banks of the Hugli about twenty 

 miles below Calcutta. Captain R. B. Seymour Sewell, I. M.S., has 

 recently sent us specimens from swampy pools at Calicut on the 



