C EH ION, GROUP XI. 255 



spicuously with locality and station is proven. That zoological knowl- 

 edge is increased by naming the individual colonies from every sisal 

 field and potato patch in the Bahamas, is open to question. The im- 

 portance of studying and recording the local variations is another 

 matter. The study of the variation of a species is hampered rather 

 than helped by a load of names, which exactly fit only the series of 

 shells obtained by the namer. 



The forms of C. glans fall into several general groups, the differ- 

 ential features of which are transgressed by comparatively few 

 specimens. These groups may conveniently be termed sub-species. 

 a. Outer lip reflexed, thickened on the face, generally more or less 

 beveled. 



b. Parietal callus appressed, not raised to form a ridge : 



typical glans. 

 b l . Parietal callus raised in a straight ridge or ledge. 



c. New Providence forms : sub-species coryi. 



c l . Andros forms, often bluish-white : subsp. griseum. 



-a 1 . Outer lip but little or not expanded, thin ; riblets usually nar- 

 rower : subsp. varium. 

 The species from Highborn and other keys south of New Provi- 

 dence are related to the varium type. 



Forms from New Providence. 

 Subsp. VARIUM (Bonnet). PI. 40, figs. 5-11. 



Shell rather shortly rimate, cylindric, the terminal cone rather long 

 and gradually tapering. White or cream-white, very irregularly 

 striped and maculate with dark brown, and usually with some ochre or 

 yellowish-brown streaks or patches. Sculpture of close, Jine riblets 

 throughout, usually a little narrower than the intervals, and about 

 25 to 30 in number on the penultimate whorl, the greater number 

 typical. Whorls 10 to 12, nearly flat. Aperture angularly ovate, 

 usually dark brown or dull lead-color within; peristome whitish, 

 very narrowly expanded, the margins connected by an almost straight, 

 raised ledge or cord acro-s the parietal wall. Parietal lamella 

 strong, short; axial lamella minute. 



Length 25, diam. 10 mill. (Bonnet's type). 



Length 22, diam. 10 mill. 



Length 20J, diam. 8^ mill. 



Bahamas : New Providence at Nassau (Swift, J. J. White and 

 others). 



