THE PERMO-CARBONIFEROUS AMMONOIDS OF .THE 



GLASS MOUNTAINS, WEST TEXAS, AND THEIR 



STRATIGRAPHICAL SIGNIFICANCE 



By Emil Bose 



PREFACE 



Permo-carboniferous fossils have been first collected in the Glass 

 Mountains, or Sierra del Vidrio, by R. T. Hill. These were described 

 and listed by G. H. Girty^ in 1908. They contained a number of For- 

 aminifera, Bryozoa, Corals, Brachiopoda, Pelecypoda, and Gastro- 

 poda, but no Cephalopoda. Hill did not try to subdivide the beds, but 

 most of the fossils seem to have come from our Word formation, al- 

 though some may have been collected in lower horizons. It is im- 

 possible to ascertain the exact localities where those collections were 

 made, Hill's references being altogether indefinite. 



In 1904 and again in 191 1, Dr. J. A. Udden made' a brief visit to 

 Marathon, Brewster County, and collected a number of fossils in 

 the region of Altuda Mountain, and among them several ammonoids. 

 In 1914 he spent three months in the Glass Mountains and con- 

 structed a series of cross sections through the Perm'o-Carboniferous, 

 collecting at the same time numerous fossils, carefully noting their 

 position and locality. In the course of this work he discovered many 

 rich fossil localities, which later on proved to be of the greatest im- 

 portance. In 191 5, Dr. Udden asked me to make a general cross- 

 section through the Permo-Carboniferous of the Glass Mountains, 

 beginning at the Cretaceous where it overlies the youngest portion of 

 the Palaeozoic, and ending in the oldest beds at the foot of the moun- 

 tains bordering the Marathon basin. He proposed to make this 

 section along the Gilliam Canyon, as this region seemed to offer the 

 greatest facilities for observation, and to continue it in the same gen- 

 eral direction south of the head of the canyon. 



I executed this work in part of September and October, 1915, with 

 the assistance of Mr. W. F. Bowman, who did the necessary topo- 



'Girty, Guadalupian Fauna, p. 27. 



