198 Annals of the South African Museum. 



Occurrence. H. baini has been found at localities on the Zwart- 

 kop's and Sunday's Eivers, and its occurrence in the Zwartkop's 

 Eiver Valley below Uitenhage has been noted by Messrs. Eogers and 

 Schwarz.* Specimens in the collection of the Geological Society 

 (Sharpe's type, registered 10976A) and in the British Museum 

 (registered 52052) are from the Sunday's Eiver. 



Remarks. Neumayr thought H. baini to be most closely related 

 to H. schenki (Oppel),t from the Spiti Shales of Tibet, and there is 

 indeed a great resemblance between the two in all the more impor- 

 tant features ; but H. baini is more closely ribbed, and as mentioned 

 by Uhlig, J in regard to the fineness of the ribbing, H. schenki 

 occupies a position just midway between H. baini and H. atherstoni. 

 Neumayr and Uhlig also thought close relationship to exist between 

 H. baini and H. keyserlingi Neum. and Uhl. from the Neocomian of 

 North Germany, but the manner of division of the ribs is really a 

 strong distinguishing feature. In H. baini none of the ribs bifurcate 

 after leaving the nodes. The relationship of H. baini to H. diptychus 

 (Keys.) and H. polyptychus (Keys.) || from Petschora-Land is also no 

 doubt much more remote than Neumayr supposed, and these forms, 

 as well as H. keyserlingi, clearly do not belong to the same division 

 of the Holcostephani (sensu lato) as H. baini and H. schenki. 

 Nikitin,^F in fact, has strongly criticised Neumayr's suggestion of 

 relationship between H. schenki and these two ammonites from 

 Petschora-Land, and Pavlow has also referred to this matter.** 



Eemarks on the points of resemblance between H. baini and 

 H. rogersi sp. nov. will be found appended to the description of the 

 latter given in these pages. 



Neumayr ff dealt fully with the question of a suggested resem- 

 blance between H. baini and a Jurassic ammonite from Madagascar 

 ascribed to J. Sowerby's Ammonites herveyi,'H and showed that these 

 really have no significant characters in common. The points of 

 resemblance are in fact so slender as not to merit further discussion 

 here ; but it may be remarked that Neumayr probably misrepre- 

 sented the case when he wrote as follows : " Newton thinks to have 

 found close relationship between Macrocephalites herveyi from 

 Madagascar and Olcostephanus baini Sharpe from the Uitenhage 



* Eogers and Schwarz (1), p. 7. 



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



J Uhlig (4), p. 132. Neumayr and Uhlig (1), p. 156. 



|| Keyserling (1), p. 327, pis. xx., figs. 4, 5 ; xxi., figs. 1-3 ; xxii., figs. 9, 10. 



If Nikitin (1), p. 122. 



** Pavlow and Lamplugh (1), p. 488 (p. 130 of authors' copy). 



ft Neumayr (5), p. 6. +} Newton (1), p. 334. 



