74 PROCEEDINGS OF THE BALTIMORE MEETING 



between 1877 and 1880, but which had never been thoroughly studied. 

 Among other important results of this research was the erection of a new 

 family of cotylosaurs, the Limnoscelidse, to include the skeleton of 

 Limnoscelis paludis Williston. In 1912 he published, in collaboration 

 with Professor Case, a paper on the "Permo-Carboniferous of northern 

 New Mexico/^ in the Journal of Geology; he also published a general 

 review of primitive reptiles in the Journal of Morphology. In 1913 ap- 

 peared a memoir, in collaboration with Case and Mehl, on Permo-Car- 

 honiferous Vertebrates from New Mexico. The same year saw the publi- 

 cation of his important papers on the primitive structure of the mandible 

 in amphibians and reptiles and on the skulls of Arceoscelis and Casea. 

 The close resemblance of Arceoscelis to the Squamata, especially in the 

 temporal region, was noted. 



Early in 1914 came the publication on Broiliellus, one of Copers 

 "batrachian armadillos," and the fuller description of the osteology of 

 Arceoscelis, with a discussion of the relationships of Arceoscelis, the Pro- 

 torosauria, and the Squamata. He then referred Arceoscelis to the 

 Protorosauria and placed this order next to the Squamata. In the same 

 year he published a series of life restorations of some American Permo- 

 Carboniferous reptiles and amphibians. 



His principal publication in 1914 was the book on Water Reptiles of 

 the Past and Present, in which his life-work on these animals was ad- 

 mirably combined with the results obtained by other workers. Williston 

 had shown a bent for the harmonious study of form and function, of 

 structure and habit, of environment and adaptation, which he applied 

 with skill and originality to the interpretation of the highly diversified 

 forms of aquatic life. He followed Eberhard Fraas, of Stuttgart, in 

 making a special study of aquatic adaptations in the vertebrates; conse- 

 quently his book on the water reptiles constitutes one of the most impor- 

 tant contributions which we have on this subject. 



The year 1915 produced his papers on Mycterosaurus, a very interest- 

 ing reptile, that threw light on the origin of the diapsid types, namely, 

 of reptiles with tivo arches at the side of the temporal region of the skull ; 

 also on T rimer orhachis, perhaps the most archaic of the American tem- 

 nospondyls, or amphibia, with the vertebrae composed of several pieces. 

 In 1916 he published the careful description of the skull and skeleton of 

 Pantylus and of Theropleura, together with the important discussion of 

 the origin of the mammalian and reptilian types of sternum. This paper 

 was followed by the admirable Synopsis of the American Pcrmo-Car- 

 honiferous Tefrapoda, in which the principal types were illustrated and 

 careful definitions of the various groups were given. In 1917 he began a 



