Occasional Papers of the Museum of Zoology 3 



4, 5, 6) is of this exaggerated form, combining almost the min- 

 imum. The difference between this and the more typical form 

 is illustrated on the accompanying plate. 



In color the shells vary from a brown with white ribs to a 

 uniform chalky white — the latter condition probably due to 

 weathering and bleaching. Embryonic shells are horn color 

 or darker, rather fragile, and with a satin-like sheen. The 

 number of ribs on the last whorl varies from about 16 to 24, 

 of varying sizes and arrangement. In outline the whorls vary 

 from w^ell rounded to decidedly shouldered, the latter predom- 

 inating in the majority of shells. 



It may be said in general that the extremes of the series 

 depart from the typical form to such a degree that only the 

 presence of intermediate forms keeps them within the limits of 

 the subspecies haileyi. It is evident, however, that the degree 

 of variation exhibited is only in proportion to the number of 

 specimens in the lot, and does not justify selection of speci- 

 mens as typical of another new subspecies. 



