The Invertebrate Fauna of the Uitenkage Series. 201 



meat with H. baini, I am unable to arrive at a definite opinion as to 

 the nearness of its relationship to that form, and feel hardly justified 

 in proposing a new specific name. It is to be hoped that the acquisi- 

 tion of additional material may enable a more thorough comparison to 

 be made and lead to a clearer knowledge of the actual relationships. 



The specimen has much general resemblance to H. rogersi sp. 

 nov., but is more coarsely ribbed. In H. rogersi, too, the ribbing 

 shows a still greater departure from that of H. baini, in that the 

 secondary costae as they proceed from the tubercles are not truly 

 direct in their course across the periphery, but have a very sli ht 

 backward throw. 



HOLCOSTEPHANUS KOGERSI Sp. 11OV. 



Plate IX., fig. 3 ; X., fig. 2. 



Description of a Single Specimen. The shell is involute to the 

 umbilical tubercules, and the ultimate whorl is broad in section 

 and broadly rounded on the peripheral area. The umbilical wall 

 falls very steeply and the umbilical rim is bluntly rounded. The 

 primary ribs, commencing above the spiral suture, are narrow, 

 and rather weakly developed. They have a slight backward slope 

 as they are traced up to the marginal nodes. There are about 

 sixteen of these laterally compressed, not very prominently 

 developed tubercles in the ultimate whorl. From these the ribs 

 of the flank proceed mostly in groups of three, though there 

 are occasionally only two ribs terminating at a node, or a rib-ending 

 may now and then fall between two nodes. These ribs as they pass 

 from the tubercles over the peripheral area are very slightly reclined, 

 that is, have a backward slope in relation to a radius. In the 

 anterior portion of the ultimate whorl the crests of the ribs on the 

 peripheral area are separated from one another by a space of 3 mm. 



Two strongly developed constrictions are visible on the ultimate 

 whorl, and they are situated opposite to one another. The specimen 

 is entirely septate, but so preserved that the figure of the lobe-line 

 cannot be traced. 



Dimensions. 



Greatest diameter 63 mm. 



Greatest breadth of the last whorl in cross-section 40 ,, 



Height of the last whorl at the centre, in section 16 ,, 



Greatest diameter of the umbilicus, measured from the 



umbilical rim between the tubercles 25 ,, 



Occurrence. The specimen, in the collection of the South African 

 Museum, is from the Sunday's Eiver. 



