/6 CONCHOLOGIA CESTRICA. 



within bluish-white ; operculum with the centre de- 

 pressed. H. 28, W. 15, aperture H. 15, W. 9, mill. 



M. decisa. [W. G. B.] 

 Fig. 153, 



Station, creeks and ponds. Chester County; abun- 

 dant. 



Lingual Dentition of M. decisa. Operculum, of M. decisa. 



Fig, 154, Fig, 155, 



Genus LIOPLAX, TROSCHEL, 1857. 



Animal of L. subcarinata, male and female. [W. G. B.] 

 Fig, 156, 



Female. Male. 



Shell, thin, ovate, turreted ; whorls rounded, carinate. 



