128 University of Texas Bulletin 



sentative of the genus Popanoceras, which was also considered as the 

 type species by Gemmellaro, and places Karpinsky's P. Krasnopolskyi 

 in the genus Stacheoceras identifying it with St. subinterruptum Krot. 



It seems thus that the older genus Popanoceras Hyatt has been 

 definitely subdivided in two : Popanoceras with saddles divided by mar- 

 ginal lobes, and Stacheoceras with entire saddles. The Triassic 

 species which had been considered as belonging to Popanoceras, uni- 

 versally have been placed in Pa^apopanoceras Haug. 



Our material from the Permo-Carboniferous of the Glass Mountains 

 contains eight species which would have to be considered as belong- 

 ing to Stacheoceras, if we take this genus in the sense of Gemmellaro, 

 but they show such surprising difference in form as well as suture, 

 and the greater part present so well-defined natural groups, that we 

 had to separate these under new subgeneric names. It is even pos- 

 sible that these groups may be considered as genera, when our know- 

 ledge of the lowermost Permo-Carboniferous and Pennyslvanian 

 Popanoceratidae shall be increased by new species. 



For the moment being, we have described under the generic name 

 of Stacheoceras, two new species which differ widely in their external 

 form, but which, with respect to their suture, resemble the Sicilian 

 species of Stacheoceras more than any of those belonging to our sub- 

 genera Marathonites and Vidrioceras. The difference between the 

 two species Stacheoceras Bowmani and St. gilliamense^ is so great 

 that I would consider them as belonging to two different genera, 

 if it were not for our imperfect knowledge of their suture. 



Stacheoceras Bowmani nov. sp. 

 PI. VI, Fig. 57-69 



Shell discoidal with flat flanks and rounded ventral portion composed 

 of deeply embracing whorls. The greatest width lies a little above 

 the umbilical shoulder. The whorls are much higher than broad. The 

 flanks curve slightly down toward the umbilical shoulder,, the wall of 

 the umbilicus is steep but extremely narrow, the umbilicus itself is 

 narrow and shallow. There are no constrictions on the whorls, either 

 on the shell or on the cast. 



On the cast of a younger specimen (pi. VI, fig. 66) we observe 

 very faint, radiating, low, flat, and very broad elevations, perhaps 



