Oti Cretaceous Cephalopoda from Zulu! and, 245 



Pseudoschloenbachia and Ganthiericeras and Muniericeras on the 

 other. 



The uncertainty as to the presence of pre-Campanian horizons in the 

 Senoniau of Pondoland and Umkwelane Hill is an additional difficulty. 

 Though, thus, the close resemblance of the suture-line of Diaziceras 

 with that of, e. g., Lenticeras andii, G-abb sp., and L. baltai, Lisson,* 

 might be explained by the mechanical laws that govern the formation 

 of the Ammonite-septum and its edge,f yet it is curious that as 

 Lenticeras is associated with Mortoniceras te.ranum, so Diaziceras 

 occurs together with the comparable M. umkwelanense, whereas the 

 presence of Peroniceras in Zululand, and of " Pnzosia " suyata and 

 the above new form in Pondolaud, suggests that the new genus may 

 be closer to Coniaciaii genera than is here assumed. Unfortunately 

 the writer has no comparable material for dissection. 



10. DIAZICERAS TISSOTIAEFORME, nov. 

 (PI. XIX, figs. 1 a-*.) 



This species is based on a completely septate specimen (No. 5478) 

 having the following dimensions : 



Diameter . . . .80 mm. 



Height of the last whorl . 50 per cent, of the diameter. 



Thickness ., . 59 



Umbilicus .14 ,, ,, ., 



The small and deep umbilicus is surrounded by four very prominent 

 tubercles, increasing in size with age, and each connected by faint ribs, 

 with about five smaller rounded tubercles on the ventro-lateral edges. 

 The prorsoradiate processes of these tubercles towards the very sharp 

 ventral edge are very faint, so that the roof-shaped periphery is 

 almost smooth. Where the shell is preserved on the ventral edge, 

 near the end of the specimen, it follows the shape of the fastigate 

 periphery of the cast, but at the beginning of the last whorl, where 

 the peripheral character of the inner whorl is well shown, the shell 

 rises in a distinct keel above the less acute ventral edge of the cast. 

 The whorl section is polygonal, with the greatest whorl-thickness at 

 the umbilical tubercles, and the two ventral and the two lateral faces 

 concave, but the umbilical slopes convex. 



* Loc. cit. (1908), pis. xiii and xiv. 



t See the writer's " Notes on Ammonites," ' Geol. Mag./ 1919, January to 

 May numbers, and compare, e.g., the suture-lines of Pseudophacoceras (PI. XXV, 

 fig. 1 b and c), and Oxynoticeras (Pia, 1914, pis. viii-xi), or of Aconeceras 

 nisoides (Fig. B 9, p. 33) and Pseudoschloenbachia grieslachi (Fig. B 8). 



