LACERTILIA. 771 



PELTOSAURUS Cope. 



Paleontological Bulletin No. 15, p. 5, August 20, 1873. Annual Report U. S. Geol. Surv. Terrs., 1873 



(1874), p. 572. 



Premaxillary undivided, with spine ; a zygomatic, postorbital, and 

 parieto-quadrate arches. Parietal bones united. Teeth pleurodont, with 

 obtuse, compressed crowns, of similar form on all the jaw-bones. Body 

 covered with osseous scuta, which are united laterally by suture. Vertebrae 

 depressed, without zygosphenal articulation. Median hexagonal dermal 

 scuta on the parietal bone. 



There are sufficient remains of the typical species of this genus to 

 furnish a basis for an estimation of its affinities, a point of some interest, 

 as this has been seldom if ever done in the case of a terrestrial lizard of the 

 Miocene epoch. The primary group to which it is to be referred is not 

 difficvilt to determine.^ 



The frontal and parietal bones are each undivided, and there is no fon- 

 tanelle in either, or in their common suture.^ There is a large postfrontal, 

 and the usual cranial arches are present, and the quadrato-jugal absent. 

 The frontal possesses strong lateral inferior crests, but whether they under- 

 ai-ch the olfactory tube completely, the specimen does not show. All the 

 usual elements of the mandibular ramus are present, but the angular is very 

 narrow. The dentary does not extend behind the coronoid on the external 

 face of the jaw. The coronoid is little produced either forward or back- 

 ward above, but sends a process forward on the inner face of the dentary. 

 The splenial is well developed, but becomes very slender anteriorly ; it 

 covers the meckelian groove, except for a short space distally, where it 

 furrows the inferior aspect of the jaw. The surangular is quite peculiar; it 

 is massive, and lacks the usual deep fossa for the pterygoid muscle, and has 

 a broadly truncate superior margin. It is in the same vertical plane as the 

 dentary, and not oblique or subhorizontal as in most Gecconidce. The den- 

 tal foramen is small, and pierces its inner face. The posterior angle of the 

 ramus is broken off. 



'See the author's Osteological Characters of the Scaled Reptiles, in Proceedings Academy Philadel- 

 phia, 1864, p. 224. 



-What I originally thought was such is a foramen-like sinus in the posterior margin of the parietal. 



