6o 



PERMO-CARBONIFEROUS VERTEBRATES FROM NEAV MEXICO. 



A DESCRIPTION OF SCOLIOMUS PUERCENSIS, NEW GENUS AND SPECIES. 



By S. W. Williston and E. C. Case. 



A new genus of pelycosaurian reptiles is represented by some remains (No. 656 

 University of Chicago) found by Dr. v. Huene in the vicinity of Arroyo de Agua on 

 the Puerco in New Mexico. The specimen consists of a complete left humerus, the 

 two ends of the right humerus, the proximal end of an ulna, a nearly complete left 

 femur, the proximal end of its corresponding tibia, a centrum, and a few fragments. 



The genus is especially characterized by the unusual divergence of the planes 

 of the proximal and distal ends of the humerus. Usually, among Paleozoic reptiles, 

 the plane of the proximal end diverges from that of the distal at an angle of from 

 45 to 60 degrees, though in some cases the two planes are at nearly right angles 

 with each other. In the present specimen the proximal end is turned outward 

 much more than a right angle, perhaps 125 degrees, to such an extent, indeed, that 



FiG. 37. Sroiioiiius p:<cneiisis, X J^. A, left humerus, radial side; B, left humerus, ventral side: C. left 

 humerus, dorsal side; D, left iilna, proximal end; E, left femur, ventral side; F, left tibia, proximal 

 articular surface; G, left tibia, proximal end from in front; H, a dorsal centrum, left side. 



the inner side of the proximal end is broadly visible from the dorsal side when the 

 distal end is lying horizontal, whereas in all other humeri known to us from the 

 Permo-Carboniferous the inner side is always more or less visible in this position. 

 The entepicondylar foramen is large; it is situated rather low down on the bone, 

 and is separated by a heavy bar from the inner margin. The femur is unusually 

 slender. It differs from the femora of other known Permo-Carboniferous reptiles 

 in the broad separation of the articular faces for tibia and fibula. The specimen is 

 doubtless somewhat depressed, notwithstanding which the projection of the dorsal 

 part beyond the articular surface for the fibula is unusual, and seems to indicate 

 that, in natural articulation, the leg must have been constantly and considerably 

 flexed upon the thigh. The upper end of the tibia shows the same broad separa- 

 tion of the articular facets for the leg bones. The trochanter is, for the most part, 

 unfortunately wanting in the specimen. The linea aspera is distinguishable as a 

 slightly rugose line, and is not at all prominent. 



The single centrum preserved has an imusual character in the distinct bttt 

 small parapophysial facet near its front margin. The diapophysis is not prominent. 

 The centrum is sharply keeled below. 



