6 AMERICAN PERMIAN VERTEBRATES 



thickness of about one foot over a considerable space, a few 

 hundred square feet, imbedded in red clay like that of the Cacops 

 bed. They are, unlike those of the Cacops bed, however, for the 

 most part isolated, and generally more or less free from incrust- 

 ing matrix, and usually in the most perfect preservation. Not 

 a few, however, show effects of erosion, as though they had been 

 rolled upon a beach of hard, shallow bottom. It is impossible 

 at present to determine with assurance the taxonomic position of 

 many of the isolated bones; nor can they be determined until the 

 fauna of the Texas Permian is much better known than is the case 

 at the present time. That there are representatives of several 

 new genera and species among the remains secured is practically 

 certain, but I hesitate to give names to isolated parts of the skeleton 

 unless such parts are very characteristic, rendering the species 

 recognizable in the future with certainty. The material secured 

 includes two or three hundred bones, none of them associated 

 save those of Araeoscelis. Among these I have, so far, determined 

 the following: Dimetrodon, represented by D. incisivus, and D. 

 gigas, and perhaps another species; an allied theromorph reptile 

 with a longer skull than that of Dimetrodon, but with a dentition 

 very different, an undoubted new genus; numerous vertebrae of a 

 very large species of Diadectes; numerous limb bones, girdles, etc., 

 which I refer to Clepsydrops natalis, together with others of an 

 allied more slender-limbed species; a number of vertebrae and limb 

 bones of Seymonria; a single femur of a pariotichid shown in 

 Plate XXXII, Figs. 6, 7; at least two genera of small reptiles 

 represented by numerous limb bones, etc.; and perhaps half a 

 dozen skeletons more or less incomplete, all found together in a 

 space of a few square feet, of the slender little reptile which I have 

 called Araeoscelis. Among the amphibian material, Trimerorha- 

 chis is represented by intercentra and parts of the skull; Diplocaulus 

 by characteristic skull and vertebral bones; and at least three 

 species of either Aspidosaurus or allied genera. In addition there 

 are a few spines of two types of sharks. 



The Araeoscelis material has not yet been fully prepared, but 

 I doubt not that it is sufficient to make out most of the skull and 

 skeleton characters. The skull has a single temporal vacuity of 



