The Invertebrate Fauna of the Uitenhage Series. 207 



Occurrence. In clay between two hard calcareous bands in the 

 railway cutting between milestones 24|- 24f on the Graaff-Beinet 

 railway, about three miles from Uitenhage (276). 



Remarks. The specimen here described was referred to by 

 Messrs. Eogers and Schwarz * as " an Olcostephanus . . . allied 

 to 0. athcrstoni," and it was rightly stated to be distinguished from 

 this by " being more compressed laterally, in having no umbilical 

 ribs, and in the less overlapping of the whorls." H. uitenhagensis 

 is considerably more discoidal in form, and the rate of increase in 

 the breadth of the whorl-section is much less than in H. atherstoni ; 

 the umbilicus is also very much wider and relatively shallower than 

 in Sharpe's type. The ribbing of these two forms is of closely 

 similar character, and both agree also in the very inconspicuous 

 development of constrictions. 



In the lateral compression of the shell and the fine character of 

 the ribbing, the wide umbilicus and the degree of involution, H. 

 nitenhagensis is more reminiscent of the typical H. astierianus 

 (d'Orb.) | than of some of the more coarsely ribbed and inflated 

 Holcostcphani that occur in the Uitenhage Series ; but the points of 

 distinction are so marked that a detailed comparison with H. astieri- 

 anus is unnecessary. The same remarks apply when we attempt a 

 comparison between H. uitenhagensis and H. sayn i Kilian,j the finely 

 ribbed form which was originally thought to be identical with H. 

 astierianus. In general habit there is similarity to the finely ribbed 

 H.filosa (Baumberger) from the Hauterivian of the Swiss Jura, but 

 the two forms are far from being identical. 



GENUS ACANTHODISCUS V. Uhlig. 



ACANTHODISCUS Sp. 



Description of a Single Specimen. The specimen consists of a 

 fragment of the chambered part of a large whorl. It measures 

 about 70 mm. from end to end along the periphery, and the cross- 

 section at the anterior end is 35 mm. in height and about the same 

 in breadth. The specimen is considerably weathered, and has had 

 the shell partially removed, showing here and there a portion of the 

 lobe-line and displaying the siphuncle near the posterior end. The 

 whorl is slightly flattened on the sides and evenly and broadly 



* Rogers and Schwarz (1), p. 10. f d'Orbigny (1), pi. 28, fig. 1 (1840). 



\ Kilian and Leenhardt (1), p. 976; Sarasin and Schondelmayer (1), part 1, 

 p. 38, pi. iv., tigs. 2, 3. 

 Baumberger (1), 4 er Theil, p. 31, pi. xxiii., figs. 2, 21>. 



