51 



are purely varietal, and are insensibly blended together in 

 different individuals. 



H. Legrandi (Cox). — Varies considerably in size, colour, 

 and sharpness and density of striae. I have found some 

 varieties pure white. Mr. Petterd from these considerations 

 has reduced H. Eicei and H. Onslowi to varietal rank under 

 this species. 



The following groups are also most variable in either size, 

 colour, or sculpture : — 



Group 1. — H. Jungermanniae, H. sitiens, H. Luckmani, H. 

 Hobarti, H. Morti, H. Furneauxensis. 



Group 2. — H. Halli, H. Spiceri, H. parvissima. 

 Group 3. — H. Bischoffensis, H. limula, H. Otwayensis. 

 Group 4— H. Nelsonensis, H. Dyeri. 

 Group 5. — H. Kershawi, H. Gadensis. 



In the neighbourhood of Mount Bischoff H. antialba is 

 generally of a brownish colour ; near Gad's Hill it is pure 

 white. 



Bulimus Dufresni (Leach). — This shell is noted for its 

 extreme range of variability in shape, size, markings, and pre- 

 vailing colour. The longitudinal bands of colour are its most 

 persistent feature, but these vary considerably. The Eev. J. 

 E. Tenison- Woods has written a most interesting paper, 

 with special reference to the variability of this widely-distri- 

 buted form. I think, however, that one of the variations 

 of form figured by him is due to comparison between an 

 immature and a fully-grown individual. In the young state 

 the shell is more orbicular than in the mature stage. Com- 

 parisons in general form should be made between shells 

 which have not less than five whorls. Five and a half whorls 

 indicate greatest development. 



These are the principal forms which are apt to puzzle the 

 classifier in the absence of the necessary particulars as regards 

 distribution and variability ; and the expression of the views 

 recorded in this paper, whether they meet with general con- 

 currence or not, will, I hope, be serviceable even to those who 

 may still try to adhere to the original classification where its 

 divisions are most arbitrary and perplexing. 



In regard to distribution I may state, as a general rule, 

 that the most variable species are the most abundant, and 

 appear to have the widest range in time and space. 



The following tables refer to the distribution of all the 



E 



