700 BicUetin Ameficatt Museum of Natural History. [Vol. XIX, 



The premaxillaries retain the alveoli of five teeth, and re- 

 semble the type premaxilla of Creosauriis atrox, a genus which, 

 however, has not yet been clearly separated from Allosanrns} 

 The maxillanes contain the alveoli for from i6 to i8 teeth. 

 Length, 460 mm. The nasals are remarkably elongate, 470 

 mm. (No. 666), and gradually increase in breadth posteriorly; 

 in No. 666 they are continuous back to the frontals; in No. 

 600 there is a fracture or suture above the preorbital fenestra 

 which is not observed in No. 666, and, therefore, is apparently 

 accidental. The frontals are extremely short, 140 mm. in No. 

 666, extending back to a point midway between the supra- 

 temporal fossae. The superior portion of the parietals is also 

 abbreviate, but laterally and posteriorly they form two large 

 transversely extended vertical plates constituting the crest or 

 superior and lateral portions of the occiput. The narrow 

 sii praoccipitals apparently extend partly between the parietal 

 crest above; below they are in contact with the conjoined 

 exoccipitals. The exoccipitals unite in the median line above 

 the foramen magnum and extend outward in two broad wing- 

 like plates with which the paroccipitals are coalesced. The 

 basioccipital alone enters into the prominently convex condyle. 



The lateral portions of the occipital region are formed by the 

 posterior plates of the squamosals , which fill the bordering 

 angle between the parietals and paroccipitals ; in side view the 

 squamosals are indented by a spur of the postorbito-frontals, 

 and send a descending process for articulation with the 

 ascending process of the quadratojugals. The quadrates are 

 vertically extended with a singly convex head above for a 

 jointed articulation with the squamosals, and a doubly convex 

 transversely extended distal extremity for union with the 

 articulars. The quadratojugals are placed on the outer sides 

 of the quadrates, and are shorter elements than the jugals. 

 The jugals are triradiate bones articulating with the quadrato- 

 jugals, postorbito-frontals, and prefronto-lachrymals, respec- 

 tively. The elements bounding the orbits anteriorly, uniting 

 with the jugals and maxillaries below and with the nasals and 



* This matter has been carefully discussed by S. W. Williston: 'The Dinosaurian 

 Genus Creosaurus, Marsh.' Amer. Journ. Sci., Vol. XI, 1901, p. iii. 



