CORRELATIONS 675 



In the top of the Gaptank formation and in the Wolfcamp beds of West 

 Texas, which lie in a part of the Permian geosynclinal basin, the Schwag- 

 erina fanna contains the beginnings of the typical Lower Permian fauna 

 in such forms as Fusulina aff. longissimoides, Sclnoagerina, two species; 

 Enteletes oehlerti Gemm. Geyerella? sp., Productus guadalupensis co- 

 ii Kin die anus Girty, Euomphalus aff. ponderosus M. and W., Omphalo- 

 trochus, two species. In the Wolfcamp are twelve species of Ammonoids, 

 described by Bbse, which possess Permian affinities, together with Clado- 

 poraf, Leptodus, and Aulosteges, aside from those already enumerated. 

 As a rule, it is characteristic of a number of Permian invertebrate forms 

 to show a marked increase in size over Pennsylvanian species. There is 

 also a tendency for many of them to take on specialized and even bizarre 

 forms. Some of these fossils have been mentioned above and others occur 

 in higher beds, such as Leptodus, Riditofenia, Aulosteges, and other 

 forms described by Girty, 5 together with such Ammonoids as Waageno- 

 ceras, Perrinites, Adrianites, Medlicoitia, Paraceltites, Stadieoceras, 

 etcetera, described by Bose. 6 



From these data it is apparent that the Schwagerinas occur at nearly 

 the same horizon as the known beginning of the Permian ammonoids and 

 in the same beds with other known Permian invertebrates. Based upon 

 its invertebrate fauna, the Neva limestone of Kansas, with its Schwag- 

 erina fauna, may be regarded, in the light of our present knowledge, as 

 forming the base of the Permian beds in Kansas, and the Schwagerina 

 beds of the same age in West Texas may likewise be regarded as marking 

 the base of the Lower Permian beds there. 



The top of the Cisco in northern Texas reaches practically to the base 

 of the Schwagerina beds, though species of this genus have not yet been 

 found there. Evidences of unconformity have been observed at this level 

 by at least three experienced geologists, though, so far, no publication to 

 that effect has come to hand. Confirmatory to these observations is the 

 fact that the usual Fusulina succession occurs to the upper Cisco where 

 the more obese Fusulinas, precursors of the Schwagerina fauna, are 

 found; but above these beds no Schwagerinas have been found, though 

 they occur in the Hueco and Marathon regions to the southwest and in 

 the Kansas- Oklahoma region to the north. It would thus seem that the 

 region now occupied by the outcrop of the top of the Cisco and base of 

 the Wichita beds that rocks of Schwagerina stage were not deposited or 

 that they were removed by erosion after deposition. However, it is more 



5 Guadalupian fauna. U. S. Geol. Survey Prof. Paper 58. 



6 The Permo-Carboniferous ammonoids of the Glass Mountains. University of Texas 

 Bulletin 1762, January, 1919. 



