The Invertebrate Fauna of the Uitenhage Series. 193 



by Karakasch, to differ from the African species by the relatively 

 wider umbilicus and less degree of involution, but to resemble it in 

 possessing backwardly inclined umbilical ribs. Kilian has described 

 an ammonite from the Hauterivian of the neighbourhood of Escrag- 

 nolles (Maritime Alps) as Holcostephanus guebhardi* and states that 

 this corresponds to H. atherstoni Karakasch, but not to the type of 

 Sharpe. In the specimen figured by Kilian the ribs of the flank are 

 strictly radial in direction, so that there is no close agreement with 

 H. atherstoni. 



Another form which may be somewhat nearly related to H. 

 atherstoni is II. schenki (Oppel), from the Spiti Shales in Tibet,! but 

 this is less densely ribbed and is further distinguished by the 

 more flattened arch of the whorl-section, and by the presence of 

 strongly marked constrictions. 



An inflated form from the so-called " Gault " on the Island of 

 Chasik and from Tukusitnu Bay (Alaska), figured by Eichwald as 

 " Ammonites astierianus d'Orb. aff." and compared by him with 

 Eoemer's Ammonites multiplicatus, may perhaps be related to H. 

 atherstoni ; but according to Eichwald's insufficient figure the 

 primary ribs are almost exactly direct (radial) in their course. A 

 complete comparison with this unsatisfactory figure is impossible, 

 since a side view only is given. { 



HOLCOSTEPHANUS cf. ATHERSTONI (Sharpe). 



A single specimen from the Sunday's Eiver, in the collection of the 

 South African Museum, agrees very closely with Sharpe's type in all 

 points except one the inflation of the shell. The whorl-section has 

 rather greater breadth in relation to its height, and the peripheral 

 area presents a more broadly rounded surface and is less highly 

 arched in sectional view than that of H. atherstoni. The shell 

 accordingly retains a rather more globose aspect, the flank of the 

 whorl is less extensive and less flattened and becomes more insensibly 

 merged in the broad peripheral area, while the umbilical cavity is 

 correspondingly rather more profound. The dimensions of the 

 specimen, which comprises a considerable -part of the body- 

 chamber, are as follows : 



Greatest diameter 130 mm. 



Greatest breadth of the last whorl in cross-section 



(estimated) 95 



* Kilian (4), p. 866, pi. Ivii., figs. 2a, 2&. 



f Oppel (2), p. 286, Tab. 81, figs. 4a-4c; Uhlig (4), p. 130, pi. xviii., figs. 2a-2c. 



+ Eichwald (2), pi. viii., fig. 13. 



