194 Records of the Indian Museum. [Vol. XIX, 1920.] 



the two main folds ma}' also assist in cleaning the foot and head as 

 they are retracted. It is possible, therefore, that whereas, as is 

 clearl}?- the case, the whole structure is protective in function in 

 Clausilia, in Ennea it assists in active aggression. The case is all 

 the more remarkable in that Ennea belongs to a family (the Testa- 

 cellidae) in which the shell is often completeh^ degenerate ; but it 

 is perhaps more common ' than is generally realized to find animals 

 of similar habits and related structure adopting in the course of 

 evolution diametrically opposite methods of improving their means 

 of attack or defence. 



i See Annandale, Jour. As. Soc. Bengal (n.s.), iX, p. 75 (1913) ; Mem. 

 Ind. Mas. V, p. 54 (1915) and Mem. As. Soc. Bengal, \'\. pp. 1Q6-197 (1918) 

 and Prashad, Rec. Ind. Mus. XVI, p. 401 (1919). 



