32 University of Texas Bulletin 



ing sandstones of the Artinsk are younger than the Sosio beds. I have 

 tried to show in our chapter on Medlicottia that NoetHng over-esti- 

 mates the value of certain details in the sutural line. The differences 

 between the species of Medlicottia are in reality so small that a deter- 

 mination of age based on the development of the sutural line is cer- 

 tainly out of the question until we get to know more material in 

 different horizons. 



Sicanites has been found in Sicily in only two species, one of which 

 is somewhat doubtful, and the type species appears to have been found 

 in only a very few specimens. Karpinsky even doubts that Sicanites 

 represents a final stage of development and thinks that the specimens 

 described as Sicanites may be nothing more than young individuals 

 or inner whorls of Medlicottia. If Sicanites is really a genus it pro- 

 bably occurs both in the Russian Artinsk {Medlicottia Karpinskyana 

 Krotow) and in the Sosio beds of Sicily. 



This comparison of the ammonoid fauna of the Artinsk and the 

 Sosio beds shows us quite clearly that the Artinsk contains a number 

 of rather archaic genera unknown in the Sosio beds or represented by 

 an occasional species. On the other hand, the Sicilian fauna contains 

 some highly developed forms, especially those belonging to the Cyclo- 

 lobinae (Hyattoceras, Waagenoceras) which are absolutely unknown 

 in the Artinsk and which find their nearest relations in higher strata 

 of the Permian. 



These facts can be deduced from the table B published by 

 Karpinsky (1. c, pp. 88, 89), and, they are still more evident if we add 

 to it those species described by Tchernow and make the necessary cor- 

 rections of generic determinations for some of the species described by 

 Karpinsky. They can only be explained by supposing that the Artinsk 

 and the Sosio beds represent paleontological zones of different age, 

 and that the Artinsk is decidedly older than the Sosio beds. 



Karpinsky obtained quite similar results. He also believes that the 

 Artinsk is somewhat older than the Sosio beds but he does not think 

 that the difference is very great (Karpinsky, loc. cit., table C on page 

 94) ; and Tschernyschew even thinks the difference in age is entirely 

 inconsiderable (Tschernyschew, Die obercarbonischen Brach. d. Ural 

 u. d. Timan, p. 720-721). 



