The Invertebrate Fauna of the Uitenhage Series. 205 



Pavlow,* but a reference to Uhlig's f description and figures of 

 Holcostephanus spitiensis shows this to have been an error. Pictet's 

 figure represents an inflated form which has some resemblance to 

 H. modderensis, but it differs from this by its relatively higher 

 whorl-section, less strong involution, and greater number of umbilical 

 ribs. Here again, the comparison cannot be quite satisfactorily 

 made, because Pictet's figure is drawn in half the natural size, 

 and the original specimen would have attained a stage when its 

 dimensions were almost twice those of the individual of H. 

 modderensis compared. 



It is also difficult to make comparison with the small inflated 

 specimens from Berrias (Ardeche) figured by Pictet under the name 

 Ammonites astierianus.\ These might conceivably represent an 

 earlier stage in the growth of such a form as H. modderensis, but 

 if this be the case some changes in the degree of involution and in 

 the form of the whorl-section would have to follow. While of 

 apparently very similar type to H. modderensis, at the stage repre- 

 sented in Pictet's figure the involution is less strong and the whorl 

 more highly arched in section, and relatively narrower. Pictet's 

 " Variete No. 3," from the same place, while possessing a broad 

 and depressed whorl-section, is still more strongly distinguished 

 from H. modderensis by the much wider umbilicus and the 

 diminished involution. The specimens represented in Pictet's 

 plate 17, figs. 3 and 4, were considered by Pavlow to be Holco- 

 stephanus spitiensis (Blanf.), but I believe this view to be erroneous. 

 They seem to me to illustrate a form probably more aptly com- 

 parable with H. modderensis than with either H. spitiensis or the 

 true H. astierianus with which they were at first identified. 



An ammonite from the Tithonian cf Stramberg, figured by Zittel|| 

 under the name Ammonites grotianus Opp., and thought by Pavlow 

 to represent Holcostephanus spitiensis (Blanf.), is believed by Uhligli 

 to be distinct from both of these and to stand nearer to the true 

 " Astierice." It has a whorl-section and inflated form somewhat 

 resembling that of H. modderensis, but it is a more widely umbilicate 

 shell, and at the stage of growth represented in Zittel's figure there 

 is a marked difference in the relation of the secondary ribs to the 

 umbilical tubercles. 



* Pavlow and Lamplugh (1), p. 497 (p. 139 of authors' copy). 



t Uhlig (4), p. 89, pi viii., figs. 1-3. 



t Pictet (1), p. 86, pi. 17, figs. 3, 4. 



Pictet (1), p. 86, pi. 18, fig. 3. 



|| Zittel (3), p. 90, pi. 16, figs. 3, 4. 



IF Uhlig (4), p. 94. 



