6 University of Texas Bulletin 



graphical work and helped me to collect fossils. The section was 

 made following generally the eastern side of the Gilliam Canyon and 

 an affluent in its upper part, crossing the Road Canyon/ the moun- 

 tains south of it, the valley between these and Leonard Mountain, end- 

 ing at the southern foot of this last-named mountain. 



After having finished this work I began to study Dr. Udden's 

 collections and found that there existed strata older than those I had 

 seen, that there existed quite a number of localities rich in ammonoids, 

 and that the Glass Mountains probably would prove one of the richest 

 localities of the earth, with respect to Permo-Carboniferous ceph- 

 alopods. 



The first fruit of these preliminary studies was a paper on the Richt- 

 liofenias found tmtil that time in the Glass Mountains and in the 

 region of the Shafter Mine (Presidio County) which was pubhshed 

 as Bulletin of the University of Texas No. 55, 191 6. 



As these first studies of Dr. Udden's collection and my own clearly 

 showed that our material for a palaeontological subdivision ^yas still 

 very incomplete, and that especially the lower part of the Permo- 

 Carboniferous was not sufficiently represented, Dr. Udden kindly 

 enabled me to make a second excursion to the Glass Mountains, this 

 time accompanied by Mr. Charles Laurence Baker, who in the year 

 191 5 had studied the older Palaeozoic and the Anthracolitic in the 

 Marathon basin, and who desired to obtain some additional data and 

 to acquaint himself with the subdivision of the Permo-Carboniferou 

 north of the Southern Pacific Railway, and to try to correlate it with 

 the strata south of that railroad, which he had studied the previous 

 year. Wt made this excursion during September and part of October 

 of the year 1916, and studied principally the lower portion of the 

 Permo-Carboniferous, although several localities of the Word forma- 

 tion were also visited, and the upper part of the Pennsylvanian, the 

 Gaptank formation of Udden. We also made a short excursion south 

 of the Southern Pacific Railway in the Mt. Ord range, where I had 

 the opportunity of seeing that the different Permo-Carboniferous 

 divisions of the Glass Mountains continue there with slight changes in 

 their lithological character. 



*0n the map of Plate 1, in Univ. of Texas Bull. No. 1753, the Road Canyon is 

 erroneously called Word Canyon, while on the geological map accompanying that paper, 

 the right name has been used. 



