34 AMERICAN PERMIAN VERTEBRATES 



Case as a distinctive one for his genus Diasparactus, but, in a large 

 species of Diadectes from Texas I do not find any appreciable differ- 

 ence in the prominence of the processes, at least in the posterior 

 presacral region. The spines are moderately elongate through the 

 series, thickened and somewhat rugose at the upper end. There are 

 large intercentra between the centra below, and as the vertebrae lie 

 in the matrix a considerable space is left between the adjacent verte- 

 brae for cartilage, indicating a very flexible, though not very firm 

 spinal column. The spines, of the posterior part of the column at 

 least, are about one inch in length. The first presacral spine is rather 

 broad and expanded above, the second and more anterior ones are 

 more slender. There is but one sacral vertebra, which has a very 

 broad, stout, sacral rib on each side, turned directly downward 

 so as to cover nearly the whole of the inner side of the ilium at 

 its junction with the ischium and pubis, its antero-posterior 

 width being 60 mm., its vertical width where it joins the ilium. 

 40 mm. The ribs immediately in front and behind are small and 

 slender and do not seem to touch the ilium at all. Case has 

 described Diadectes as having two sacral vertebrae, but in the speci- 

 men in the Chicago collections, of a large species, the structure of 

 the sacrum seems to be quite as in Limnoscelis ; and this is also 

 the case in a new genus of Diadectidae, which Professor Case 

 will describe from a specimen in the University of Chicago col- 

 lections, collected by Mr. Miller. 



The first chevron occurs at the hind end of the third caudal 

 vertebra, the first one visible above the ischia from below; the 

 first three or four of the caudal vertebrae have short free ribs, as 

 in other genera of American Cotylosauria. The tail, as preserved 

 in specimen No. 908, is rather slender, with short spines and 

 chevrons, precluding the idea that the animal was natatorial in 

 habit. The terminal vertebrae are a little elongated. 



Pectoral girdle and extremity. — The pectoral girdle lies in very 

 orderly arrangement, with little if any distortion. Both clavicles 

 are in articulation with the interclavicle, scapulae, and cleithra. 

 The clavicles have the usual cotylosaurian form, curving under 

 the anterior end of the interclavicle and the anterior margin of the 

 coracoid, curved and somewhat spoon-shaped below. The long. 



