i6 University of Texas Bulletin 



represented the upper limit of the Pennsylvanian, but Udden observed 

 in an vinnamed place which we afterwards used to call the Wolf 

 Camp (between Gap Tank and Leonard Mountain) that there were 

 certain strata below the unconformity, mostly shales and limestones, 

 which contained fossils similar to those in the Word formation — as 

 for example, Lyttonia, — and which did not seem to confirm the idea 

 that the Gaptank formation really belonged to the Pennsylvanian. 

 Near the Wolf Camp, Udden also found a few small cephalopods, ap- 

 parently belonging to new species. By studying Dr. Udden's col- 

 lections and those that were made by Mr. Charles L. Baker, and my- 

 self, at the same locality, and which contained several hundred am- 

 monoids, I was able to demonstrate that the Gaptank formation 

 really contained two different horizons, an upper one only preserved 

 near the Wolf Camp which represents the lowermost Permo-Carboni- 

 ferous, and which I shall call the Wolfcamp formation; and a lower 

 one which contains a characteristic Upper Pennsylvanian fauna, for 

 which we preserve the n'ame Gaptank formation.* The uncon- 

 formity thus does not constitute the boundary between the Carboni- 

 ferous and the Permian, but belongs to the lower part of the Permian, 

 notwithstanding that in most parts it forms the limit between the 

 Pennsylvanian and the Permo-Carboniferous. In the eastern region 

 the unconformity separates the Hess formation from the Gaptank 

 formation (Gap Tank and some miles farther west) although in one 

 place there it has eroded the upper limestones of the Gaptank forma- 

 tion. At Wolf Camp we find the unconformity between the Hess 

 and the Wolfcamp formation, but farther west, this latter one and 

 even the whole Gaptank formation are entirely eroded and the uncon- 



*Bditor's Note: The undersigned has inadvertently in his "Notes on the Geology 

 of the Glass Mountains," ("Univ. of Tex. Bull. No. 1753), himself taken the credit of 

 having named the Wolfcamp formation. I wish to state here that the- discovery of 

 the Wolfcamp could hardly have heen made except by a paleontologist of such accom- 

 plishments as Dr. Bose. The classification and subdivision of the entire anthracolitie 

 section in the Glass Mountain country was to a large extent the joint work of the three 

 authors of University of Texas Bulletin No. 44. It so happened that the writer of this 

 note had done most of the field work on the Permo-Carboniferous rocKS in the Glass 

 Mountains; Baker had no doubt the best information on the general geology of the 

 surrounding region; while Dr. Bose was relied upon for that critical paleontological 

 knowledge which is decisive in all work of this kind — a circumstance particularly for- 

 tunate for our studies in this region. 



J. A. UDDEN. 



