8 University of Texas Bulletin 



Before we enter into the disctission of our problems it remains to 

 express my warmest thanks to Dr. J. A. Udden, Director of the 

 Bm-eau of Economic Geology, for the great liberality which he showed 

 in allowing me to make use of his important and detailed field notes, 

 as well as of his collections; for his assistance in obtaining the nec- 

 essary literature and his ever-ready willingness to further my studies. 

 Neither should I forget to extend my sincerest thanks to the gentle- 

 men who have helped me to collect the fauna here described — Mr. 

 Charles Laurence Baker and Mr. W. F. Bowman; without whose 

 assistance I probably would not have been able to amass the necessary 

 material. 



I also wish to thank Mr. Carl Christianson at Austin for the great 

 pains he has taken in making the photographs of the fossils which 

 have been used for the compilation of the plates which accompany 

 this work. 



All the sutures reproduced here have been photographed with the 

 apparatus described by me about ten years ago.^ This apparatus can 

 be further improved by setting it on another slide working at right 

 angles with the one described in the article mentioned; this allows of 

 centering the fossils with flattened sides, and of using a common 

 Penny Picture Camera or holder. The circumstance that between 

 two and twenty-four pictures can be made on a plate of 5 by 7 inches, 

 results in sa\'ing plates and at the same time avoids movement of the 

 camera during the changing of the plateholders. 



Austin, Texas, January, 191 8. 



'E. Bose, Ein verbesserter Apparat zur photcgraphischen Reproduktlon von 

 Ammonitensuturen und Ambulakren von Seeigeln. Centralblatt f. Min. Geol. u. Pal., 



1907, p. 422. 



