132 SAMUEL WENDELL WILLISTON— LULL. [Memoir [ vol T xvi a i i ; 



classification is merely genealogy. It is only the paleontologist who is competent to express 

 opinions concerning the larger principles of classification of organisms, and especially the 

 classification of reptiles. The neozoologist, ignorant of extinct forms, can only hazard guesses 

 and conjectures as to the relationships of the larger groups, for he has only the specialized or 

 decadent remnants of past faunas upon which to base his opinions. 



The third chapter is an illuminating discussion of the skeleton of reptiles, in which the 

 principal elements are not only fully described, but illustrated by the author's drawings. 

 The chapter on the Age of Reptiles contains a chart (that of 1909) showing the range in time 

 of the various reptilian suborders, beginning with the Carboniferous. Each important horizon 

 is taken up in turn and the character of the sedimentation and location of the chief exposures 

 discussed. This section is illustrated by Williston's restorations of various Permocarbonif- 

 erous reptiles. 



The fifth chapter discusses the principal structural changes which water-living brings 

 about, comparing the reptiles in their modifications with other important aquatic types. Then 

 in orderly sequence the water-inhabiting groups are discussed: Sauropterygia; Lystriosaurus 

 of the Anomodontia; the Ichthyosauria, in which the culmination of aquatic adaptation is 

 reached; Mesosaurus, of the Protorosauria; many of the Squamata, especially the marine 

 iguana, Amblyrhynchus ; and the agialosaurs and mosasaurs. 



Another chapter treats of the Thalattosauria, recently described by Merriam, and of 

 Champsosaurus of the Rhynchocephalia. Crocodile-like forms are included under two orders, 

 Parasuchia and Crocodilia, Geosaurus, an upper Jurassic crocodile, going to the extreme and 

 developing an ichthyosaur-like tail for swimming. The final chapter discusses the Chelonia, 

 the most sharply distinguished order of reptiles, and the one which has had the most uniformly 

 continuous and uneventful history from the Triassic up to the present time. 



In " Restorations of some Permocarboniferous Amphibians and Reptiles," 1914, 121 Wilhston 

 presents some interesting interpretations in the flesh of these ancient tetrapods, drawing them 

 personally after a careful study of the more or less complete skeletons in the collections of 

 the University of Chicago, the American Museum, and Yale University, the technical descrip- 

 tions of which had recently been published. Of these he says (p. 57) : 



I will not attempt to give any technical details of their structure here; my only desire is to place before the 

 general student of geology something of what I see, after years of study of the fauna, in some of the animals that lived 

 in Texas and New Mexico during the closing times of the Pennsylvanian and the early times of the Permian. The 

 land vertebrate fauna of those times in America must have been very rich. More than 40 distinct genera of amphi- 

 bians and reptiles are represented in the collections of the University of Chicago, and the remains of at least a dozen 

 more are preserved in the American Museum and at Yale University. It is the oldest fauna of reptiles known in the 

 world, and by far the most comprehensive of the older amphibians known. The animals of the South African Karoo 

 system are nearly all of later age, upper Permian as distinguished from lower Permian and Carboniferous, and they 

 were, for the most part, more highly specialized and less primitive. 



Williston says, in conclusion, that whatever may be the merits of these restorations as 

 works of art, they have been drawn with the most scrupulous accuracy so far as form and 

 proportions are concerned, the musculature derived from the study of living reptiles, and they 

 are all based upon practically complete skeletons; in a few only the precise length of the tail 

 is yet unknown, or the front toes. 



In 1915 Williston described Trimerorhachis insignis, a temnospondylous amphibian, from 

 abundant material; 123 two genera of Permian reptiles, Glaucosaurus, with immense orbits, 

 and Chamasaurus of the slender jaw; 123 as well as a new genus and species, Mycterosaurus 

 longiceps, a pelycosaur related to Dimetrodon. 121 



Several papers of importance appeared during 1916. In Part II of the "Osteology of some 

 Permian Vertebrates," 130 Williston describes in detail the curious Pantylus from Texas, which 

 as he says, is, so far as his knowledge goes, the earliest reptde in geological history having a 

 bony dermal armor. Isodectes is also further discussed, and the species Theropleura retroversa 

 Cope, which had been known from the centrum of a single vertebra, is now described prac- 

 tically in toto. The ventral ribs of this form are very remarkable, numbering some 200 on a 



