C EH ION, (iROLl' 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 O. 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. 

 ^.Parietal callus raised in a straight j-idge or ledge. 



c. New Pro.vidence forms : sub-species coryi. 



c 1 . Andros forms, often bluish-white.: suhsp. 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, fine 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 across the parietal wall. Parietal lamella 

 strong, short; axial lamella minute. 



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



Length 22, diam. 10 mill. 



Length 20^, diam. 8 mill. 



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

 others). 



