academy op sciences.] PUBLISHED RESULTS. 129 



Of it Williston says (p. 279) : 



The creature as mounted presents an almost absurd appearance, with its large head and pectoral region, absence of 

 neck, and short tail. It is very certain that it possessed no other dermal ossifications than those of the median dorsal 

 carapace, and it would seem almost as certain that the creature was aquatic or largely amphibious in its habits. * * * 

 What the significance of the dermal carapace was I am at a loss to suggest. That it could have been of protection to the 

 creature seems more than doubtful, whatever may have been its use in Dissorophus, where it covered the whole dorsal 

 region. But this coincidence is remarkable; with an external turtle-like ear opening, it had also the beginning of a 

 turtle-like carapace. And this parallelism is also seen in Diadectes [this it will be remembered is an amphibian], with 

 dorsal dermal plates and turtle-like ears. * * * Whatever may have been the habits of the creature, it, with its 

 nearly related Dissorophus, must be classed among the oddities of vertebrate paleontology. 



In his paper on new Permian reptiles, 1910, 96 WiUiston describes in part the material taken 

 from the so-called Craddock bone bed, discovered by Paul Miller in the autumn of the previous 

 year on the Craddock ranch near Seymour, Tex. These fossils include a great variety, among- 

 which was the type of Arseoscelis gracilis and of a new family, the Arseoscelidse. He also 

 discusses the problem of the development of the holospondylous vertebra, which has given 

 rise to much contention among paleontologists, and of which he wrote in detail in the last year 

 of his life. 



In the next year, 1911, came the publication of an important book, "American Permian 

 Vertebrates." 10 ° This, as the author says, comprises a series of monographic studies, together 

 with briefer notes and descriptions, of new or little-known amphibians and reptiles from the 

 Permian deposits of Texas and New Mexico. The sources of the material are mainly three — 

 the University of Chicago collection, made in recent years by field parties under the charge 

 of Paul Miller or the author; earlier collections of the University of Texas, made by Prof. 

 E. C. Case; and finally, the Permian fossds in the Marsh collection at Yale, many of which 

 were unknown to science untd brought to light for study by Prof. Williston. An interesting 

 comment upon our knowledge of reptilian classification shows that the time is not yet ripe to 

 attempt phylogenies of the groups other than the dinosaurs, crocodiles, phytosaurs, pterosaurs, 

 and rhynchosaurs, because we are less sure of them than we were a dozen years ago. The 

 more recent general classifications of the reptiles by Cope, Osborn, Boulenger, and others have 

 offered suggestions of value, but are by no means the real solutions of the reptilian and am- 

 phibian phylogenies. Certain morphological problems are discussed in the following pages and 

 the author has given what seem to be the legitimate conclusions regarding the immediate 

 relationships of the forms under discussion. The present work, however, is offered more as a 

 contribution to our knowledge of ancient reptiles and amphibians, with such summaries and 

 definitions, based chiefly upon American forms, as the evidence at hand permits. A summary 

 of the genera from the Texas Permian follows: 



Amphibia: Lysorophus, Diplocaulus, Trimerorhachis, Eryops, Cacops, Dissorophus, As- 

 pidosaurus Cardiacephalus. 



Reptilia: From the uppermost beds, Labidosaurus, Naosaurus, Dimetrodon, from lower 

 horizons, Naosaurus, Dimetrodon, Clepsydrops, Varanosaurus, Trispondylus, Casea, Arseoscelis, 

 Captorhinus, Diadectes, Seymouria, etc., of which perhaps the most characteristic are Labi- 

 dosaurus of the upper and Cricotus of the lower zone. 



Williston feels confident, however, that no definite line can be made between the two 

 divisions, and that at present Clear Fork can be used in a general way to designate the upper, 

 and Wichita the lower part of the Texas deposits. 



In the paper on Permian reptiles, published in Science in 1911, 104 Williston proposes a classi- 

 fication for the therocrotaphic reptiles (excluding the Theriodontia) : Order Theromera [later 

 he uses the spelling Theromorpha] ; suborders Pelycosauria, Poliosauridas, Edaphosauridse, 

 Caseidse, Ara3oscelidse(?), Therocephalia, Anomodontia, Dinocephalia, and Dromasauria, the 

 first five American, the others African. In his restoration of the cotylosaur Seymouria in 

 the same year, 101 he makes known to us, aided by a very accurate drawing, the complete 

 osteology of the creature that stands lowest in rank among reptiles, approaching in 

 many ways the contemporary amphibians, for, as he says, so far as the characters are 



