174 Annals of the South African Museum. 



of the aperture is a well-developed callus. There is a slightly 

 developed, short, closed umbilical slit. 



Dimensions. (I) (2) (3) 



Height of the shell 11 . 12 . 13mm. 



Height of the body- whorl at the aperture 8 8 . 9 ,, 



Greatest width of aperture 6 . 5-5 . 6 ,, 



Occurrence. Found by Mr. Eogers in the cliff on Buck Kraal, 

 Sunday's Eiver (136h). 



Remarks. This form is distinguished from small specimens of 

 Natica uitenhagensis sp. nov. by the rather more expanded and less 

 elevated figure of the shell, and the broader and more rounded form 

 of the aperture. A specimen from the neighbourhood of Uitenhage 

 (350), ascribed above with some doubt to N. uitenhagensis, is com- 

 parable in point of size with individuals of N. rogersi. It differs 

 from these by its broader apical angle, shorter spire, narrower and 

 more elevated figure, and relatively higher body-whorl and aperture. 



NATICA ? MIBIFICA sp. nov. 

 Plate VIII., figs. 14, 14a. 



Description. The shell consists of at least six whorls, and has a 

 somewhat elongated turbinate outline with the body-whorl well pro- 

 duced and narrowed below. The body-whorl overlaps about half 

 the preceding whorl, and occupies rather less than two-thirds of the 

 total height of the shell. The spiral suture is well impressed, and 

 below it the whorl-surface bulges out in the form of a convex spiral 

 fold. Immediately below this rounded swelling of the whorl-surface 

 is a depression of the surface forming a concave spiral band. This 

 impressed zone is less well developed in the earlier whorls, more 

 pronounced in character in the later ones. At the middle zone of 

 the whorl the surface is again convex, and below this the whorl- 

 surface slopes inwards with less marked convexity. The concave 

 and convex zones in the upper half of the whorl merge into one 

 another without the production of any angularities of the surface 

 or of the outer lip of the aperture. 



The shell-wall is moderately thick. The surface is smooth and 

 only marked by transverse growth-lines. The spiral angle is about 

 70. The aperture is elongated, its height being about twice as 

 great as its maximum breadth. It is angular at its upper extremity 

 and has a narrowed, rounded outline below. The inner lip is 

 thickened and a callus is developed. There is a short, narrow, 

 but closed umbilical slit. 



