1 6 AMERICAN PERMIAN VERTEBRATES 



men; olecranon moderately produced. Four bones in the proxi- 

 mal row of the carpus; two free centralia, and five carpalia; 

 hand pentedactylate; two bones in proximal row of tarsus, a 

 single centrale and five tarsalia; feet pentedactylate; phalangeal 

 formula, usually, if not always, 2, 3, 4, 5, 4 (3). Anterior ribs 

 dilated and overlapping in all known American forms. 



Family Diadectidae 



Cope, Proc. Amer. Phil. Soc, XIX, 45, 1880; Marsh, American Journal of 

 Science, XC, 410, 1878 (Nothodontidae). 



Skull short and high, very rugose above; parietal foramen very 

 large; prefrontals and postfrontals meeting broadly over orbits; 

 a broad and rather deep otic emargination in posterior temporal 

 region. The single row of teeth in maxillae and dentaries deeply 

 thecodont, with narrow, transverse crown (except the most anterior 

 ones) showing a median cusp and a lateral lower one on each 

 side. A vestigial cleithrum present; vertebrae with thick, stout 

 spines; one or two sacral vertebrae present; usually a hyposphene 

 and hypantrum. Tail moderately long or short. Legs short and 

 stout; carpus and tarsus fully ossified, the proximal carpal and 

 tarsal bones relatively small; ungual phalanges broad and flat; no 

 ventral ribs. 



NOTHODON 



Marsh, American Journal of Science, XV, 410, May 3, 1878; ? Diadectes Cope, 

 American Naturalist, XII, 327, 1878 (published April 22, fide Cope); 

 Proc. Amer. Phil. Soc, XVII, 205, 1S78; Paleontological Bulletin, No. 

 29, 1878 (published May 8, fide Cope). 



Nothodon lentus Marsh, op. cit. Plate XXXIV, Figs. 5-7; Plate 

 XXXV, Figs. 1-4; Plate XXXVI, Fig. 2. Rio Arriba 

 County, New Mexico. Yale Museum. 



This genus of reptiles may readily be distinguished by the dentition. In 

 each separate premaxilla there are two slender pointed teeth. In front of the 

 maxillary there are one or two smaller teeth, followed by a number with 

 transverse crowns, resembling in form the premolars of some carnivorous 

 mammals. These crowns, when unworn, have a central cusp, and on each 

 side a tubercle, somewhat like that on the premolars of the genus Canis. In 



