192 Annals of the South African Museum. 



Africa. The specimen is preserved unfavourably for an exhaustive 

 comparison, but certainly bears a very close resemblance to H. 

 atherstoni, particularly in the inflation of the whorls and the general 

 character of the ribbing. Some readily apparent differences may at 

 the same time be noticed. At a comparable stage of growth the 

 Speeton form is distinctly more closely and more delicately ribbed ; 

 umbilical ribs are hardly denned, and certainly have not attained the 

 development to be observed at a similar stage in H. atherstoni. A 

 further point is that in all specimens of H. atherstoni the flattened 

 umbilical marginal tubercles have either a slight backward direction 

 when traced towards the flank, or their disposition is strictly radial ; 

 in the Yorkshire example, on the other hand, the tubercles have a 

 strong forward inclination. These differences cannot be overlooked, 

 and they strongly suggest that the Speeton form may not be 

 identical with that from South Africa ; but it must be admitted that 

 the two approximate very closely to one another. It may suffice to 

 have drawn attention to these points of difference while refraining 

 from any final expression of opinion concerning the intimate relation- 

 ship of these forms a question which can only be ultimately settled 

 by the comparison of further material. At the same time, I am 

 inclined to think that the Speeton form will not be found to be 

 identical with H. atherstoni. 



Other finely ribbed specimens from the lower part of the zone of 

 Belemnites jaculum at Speeton, which have been referred by Prof. 

 Pavlow and Mr. C. G. Danford to Holcostephanus astierianus (d'Orb.), 

 are also in some respects comparable with H. atherstoni ; but they 

 are usually of small size, and a satisfactory comparison with the 

 much larger available examples of H. atherstoni is difficult. One 

 such individual, in which the development of constrictions does not 

 form a feature, has been figured by Mr. Danford under the name 

 Olcostephanus (Astieria) astieri.* It is laterally compressed and 

 relatively highly arched, and the umbilical ribs are very weakly 

 developed and are not backwardly inclined. The secondary ribbing, 

 which is of a very crowded and delicate character, has a stronger 

 forward inclination than that of H. atherstoni. The tubercles also 

 have a forward inclination, which is not the case in the African 

 species. 



Karakasch has described a Holcostephanus from the Lower 

 Cretaceous of Biassala (Crimea) under the name Holcostephanus 

 (Astieria) cf. atherstoni Sharpe.f It appears, from the figure given 



* Danford (1), pi. xi., figs. 7, la. 

 f Karakasch (1), p. 103, pi. i., fig. 3. 



