PENNSYLVANIC-PERMIC PERIOD 561 



faunas of the West have often a facies which is novel and perplexing to one 

 familiar only with the well known Eastern ones; and it is probable that the 

 lowest faunas of this region will in many cases prove to be of Pottsville age. 

 .. . . The resemblances to the fauna of the Morrow formation . . . are 

 sufficiently numerous and striking to make this a very promising hypothesis. 



"It will be remembered that C. D. Walcott described an interesting fauna 

 from the Eureka district, in which there was found a commingling of Upper 

 and Lower Carboniferous types. This is likely to prove of Pottsville age. 

 The lowest Pennsylvanian faunas of Colorado and of New Mexico, especially 

 the latter, also show similarities which appear to me highly significant. The 

 Bend and Milsap formations of Texas may likewise prove to be Pottsville" 

 (Girty, 1905: 10). 



The following are some of the more characteristic fossils of the Potts- 

 villian (A = Appalachian region, W = Southwestern and Western, no 

 letter = both regions) : Triticites secalicus, Lophophyllum sauridens 

 (W), Cystodictya carbonaria (A), Rhipidomella pecosi (W), Chonetes 

 mesolobus, C. platynota (W), Pugnax rocky montana (W), Productus 

 longispinus, P. muricatus, P. nebrascensis, Spirifer cameratus, S. rocky- 

 montana, Spiriferina kentuckyensis (W), Hustedia mormoni (W), 

 Cleiothyridina roisii (W), Composite/, subtilita, Squamularia perplexa 

 (W), Dielasma millepunctata (W), Aviculopecten occidentalis (W), A. 

 ■coxanus, A. hertzeri (A), A. whitei (W), A. interlineatus (A), Pinna 

 per acuta, Aviculopinna americana (A), Astartella vera, A. varica (A), 

 Macrodon obsoletus, M. carbonarius, M. tenuistriatus (A), Schizodus 

 sub circular is, S. affinis, Lima retifera, Bellerophon percarinatus (A), 

 Patellostium nodocostatum (W), Euphemus nodocarinatus (A), E. car- 

 bonarius (A), Stearoceras gibbosum (W). 



In the Bend of Texas occur Goniatites striatus, G. crenistria (both 

 occur lower in shales correlated by J. P. Smith with the Batesville or 

 Fayetteville of Arkansas), Gastrioceras entogonum (also in Fayetteville), 

 G. compressum, Paralegoceras iowense (also in "Coal Measures" of Iowa), 

 P. texanum, Metacoceras walcotti, and Stearoceras gibbosum} 11 Accord- 

 ing to Cummins, 178 there are also included Hadrophyllum aplatus, Cho- 

 netes mesolobus, Productus nebrascensis, Spirifer cameratus, Myalina sub- 

 quadrata, Euphemus carbonarius, etcetera. Ulrich 179 likewise regards the 

 Bend as of early Pottsvillian time. 



According to paleobotanical evidence the Pottsvillian, together with the 

 Allegheny, "approximately represents the Westphalian or Muscovian" of 

 Europe. "The Westphalian is the period of Cheilanthites, Mariopteris, 



177 Smith : Monograph 42, TJ. S. Geological Survey, 1903. 



178 Cummins : Second Annual Report of the Geological Survey of Texas, 1891, p. 366. 



179 Ulrich : Professional Paper no. 24, U. S. Geological Survey, 1904, p. 111. 



