56 HENRY CLIFDEN BUBNUP. 



small basal tooth-like plait arises but little within the edge of 

 the peristome at the base of the columellar lip and curves 

 inwards and upwards slightly to the left. The process on the 

 columellar lip, which I have above called " a broad, slightly 

 raised, rounded tooth/' consists of an inward bend of the lip 

 covered by its outward expansion, and is quite superficial. 

 The deep-seated columellar fold, which is wholly internal, is 

 rounded in outline, scoop-shaped, and presents its right, lower 

 edge furthest forward. The ridge across the base is very 

 inconspicuous, and might easily be overlooked ; its position, 

 however, can be traced on the outside by a slight corrugation. 

 The positions of the other processes, except the parietal, are 

 also indicated externally by corresponding depressions. The 

 peristome, which is comparatively but little thickened, is 

 exceedingly sinuous on the labrum (fig. 22). From the rima 

 there is a deep opening passing into the columellar fold, but 

 none can be detected into the axial perforation. 



Besides those of the type the following dimensions of 

 normal specimens have been taken : Dargle : height x width, 

 2-12 X 0-88, 2-10 X 0-88, 2-05 x 0-89. Nottingham Road: 

 2-04 X 0-89, 2-07 x 0-89, 2-00 x 0-91, 1-94 x 0-89 mm., and 

 the following are the dimensions of the largest and smallest 

 examples in my collection, both manifestly abnormalities : 

 Nottingham Road, 2-60 x 0-91 ; Dargle, 1-83 x 0-93 mm. 



This shell has been confused with B. sylvia M. & P., but 

 though the armature of the aperture is arranged much on the 

 same plan, only one plait differing very materially, this fact, 

 I think, must be taken as an indication of parallel develop- 

 ment rather than close affinity, for in all other important 

 respects the two species vary widely. The form of this 

 species is elongate-oval or fusiform; that of sylvia cylin- 

 drical, with almost parallel sides. In sylvia there is an 

 umbilical opening from the rima, fairly wide for so small a 

 shell; in mel villi it seems to be closed. Mel villi has 

 rather more than half a whorl in excess of sylvia, the whorls 

 of the former being more ventricose and separated by deeper 

 sutures : with the exception of the embryonal whorls, they 



