MEMORIAL or S. W. WILLISTON 73 



Williston and Case at all times fully and cordially cooperated with each 

 other in the study of Permian reptiles and amphibians. In 1908 he pub- 

 lished an important but brief paper on the Cotylosauria, containing a 

 description of the skeleton of Labidosaurus indiisivus. In the same year 

 Mr. Paul C. Miller, of the American Museum of N"atural History, a col- 

 lector and preparator of high rank, became Professor Williston's assistant 

 at Chicago, and under his direction began a long series 'of explorations in 

 the Texas Permian, which have yielded results of the greatest importance 

 to vertebrate morphology and paleontology. During the next decade 

 these expeditions brought back to the university a great number of speci- 

 mens, some of which will become more and more famous as their great 

 importance is gradually realized. More or less complete skeletons were 

 discovered, extricated with great skill, and admirably described in a long 

 series of publications. Among the more important of the new or little 

 known skeletons were the following, which, to students of the early evolu- 

 tion of the skeleton of vertebrates, will ever stand as important types : 



Pariotichus laticeps Williston 

 Trematops milleri Williston 

 ArcBOScelis gracilis Williston 

 Seymouria T)aylorensis Broili 

 Casea hroilii Williston 

 Mycterosaurus longiceps Williston 

 Trimerorhachis insignis Cope 

 Varanosaurus hrevirostris Williston 

 Ophiacodon mirus Marsh 



These were only the more conspicuous of the many priceless specimens 

 which Williston and Miller have brought to light, and which the former 

 has described and figured with the most painstaking care and accuracy. 

 This material also enabled Williston to give definite and in many cases 

 final figures of the sutural limits of the elements of the skull in most of 

 these genera. Many investigators had attempted to do this from less 

 extensive and complete material, but their results were often uncertain 

 in detail and subject to important changes and corrections. 



In 1911 he published from the University of Chicago press his volume, 

 American Permian Vertebrates, which comprises a series of monographic 

 studies on some of the genera already noted. This work contains many 

 new and original plates. Careful and extensive definitions are given of 

 the orders Temnospondyla, Cotylosauria, Theromorpha, and of the in- 

 cluded families and genera. In the same year, by invitation of Professor 

 Schuchert, Williston examined and described the important collection of 

 Permian reptiles which Mr. Baldwin had collected for Professor Marsh 



