[46 University of Texas Bulletin 



because there the first auxihary lobe is on the umbiHcal shoulder, while 

 in ours the second auxiliary lobe occupies that place. St. Parkeri 

 seems to dififer also from the Russian species mentioned above. Ac- 

 cording to Karpinsky's Fig. 5a, there are probably more lobes on the 

 ventral side and the flanks than in the American species, and the septa 

 are certainly less near together. 



Smith^ remarks that the bed in which St. Parkeri has been found 

 belongs to the middle Coal Measures (Strawn formation), and that 

 Freeh wrongly refers these beds to the Permian. Freeh probably 

 followed Karpinsky, who, in his Table C (loc. cit., p. 94, and on p. 

 92, 93), places these beds in the Permo-Carboniferous. 



Age: 



The only specimen was found by myself on the ranch of Mr. Hargis 

 near Marathon. It was found loose on rocks of shale of the Pennsyl- 

 vanian age, near the boundary line with the lower Permo-Carboni- 

 ferous. The specimen is preserved as limonite, formed by the oxida- 

 tion of pyrite. There were no more limonite shells found in the 

 Pennsylvanian ; I suppose, therefore, that this specimen rolled down 

 from the Permian which probably belongs in the Hess formation. In 

 the Wolfcamp formation, fossils composed of limonite are common, 

 but they are also found in the Hess formation (Leonard Mountain.) 



Number of specimens examined: 

 One. 



Locality: 



Anticline on Hargis's ranch near railroad milepost 580, about three 

 miles west of Marathon. 



Vidrioceras nov. subgen. 



Type: Vidrioceras Uddeni Bose 



In our description of the new subgenus Marathonites, we have tried 

 to show briefly how the original genus Popanoceras Hyatt was divided 

 into two genera by splitting off those species with entire saddles, for 

 which the name Stacheoceras was given by Gemmellaro. Furthermore, 



'J. p. Smith, Garb. Amm. of America, p. 133. 



