30 University of Texas Bulletin 



in the Sosio beds and only by one in the Artinsk. Among the Gastrio- 

 ceras of the Artinsk there are yet forms which are nearly related to 

 Carboniferous foi'ms (Gastrioceras Fedorowi, G. Nikitini) while 

 others like G. Sucssi belong to the group of G. Zitteli. In the Sosio 

 .beds the older forms seem to be absent and all the species described 

 belong to the younger group of G. Zitteli. The species described by 

 Gemmellaro as Glyphioceras have nothing to do with the Carboni- 

 ferous Glyphioceras. 



Agathiceras is about equally frequent in both faunas but the genus 

 changes very little in the dififerent horizons from the upper Carboni- 

 ferous to the different .stages of the Permo-Carboniferous and is there- 

 fore of no importance at all except on account of its greater frequency 

 in the younger formation. A higher stage is represented by 

 Adrianites and it is quite characteristic that from the Artinsk only 

 one species has been described (Tchernow cites a second one) while 

 ten are known to occur in the Sosio beds. Among these are two belong- 

 ing to the subgenus Hofmannia altogether unknown in the Artinsk. 



The genera Doryceras and Clinolobus seem to be limited to the 

 Sosio beds and are not known with certainty elsewhere. 



Very characteristic is the distribution of the different groups and 

 perhaps subgenera of Stacheoceras in both faunas. In the Artinsk we 

 find not only the type with very few lobes, similar in its external ap- 

 pearance and in its suture to those which occur in the Carboniferous 

 and which may all be nearly related to our subgenus Marathonites; 

 but also the type with a higher development of the suture. In the 

 Sosio beds only these latter forms (represented by twelve species) are 

 known to occur. Popanoceras s. s., is represented by only one species 

 in the Artinsk, while in the Sosio beds four species occur ; Popanoceras 

 certainly represents a higher stage of development than Stacheoceras 

 does. 



Very important is the occurrence of the highly developed Cyclolo- 

 binae (Hyaftoceras and Waagenoceras) in the Sosio beds. They are 

 nearly related to the evidently younger form of Cyclolobus. None of 

 this kind has been described from the Artinsk. 



In the Sosio beds, Thalassoceras is represented by four species, while 

 in the Artinsk only one or two occur, and the only one figured may 



