﻿578 silurian gasteropoda prom llano a dock. [Aug. 1905, 



.Discussion (on the two foregoing- papers). 



Prof. Groom said that students of Palaeozoic stratigraphy con- 

 stantly experienced difficulty in the determination of the imperfectly- 

 known gasteropoda so abundant in many places, and they would be 

 grateful to the Authoress for her useful contribution to the literature 

 of the subject. It was true that the studies had been made on 

 casts, and that casts were not so readily examined as fossils pre- 

 served in their original condition ; but the perfect retention of the 

 external form and minute details of ornamentation not uncommon 

 in such cases was an advantage. 



