512 GEOLOGICAL SURVEY OP THE TEERITORIES. 



LAOEETILIA. 

 PELTOSAURUS, Cope. 



Palentol. Bulletin, No. 15, p. 5. 



Premaxillary undivided, with spine; a zygomatic postorbital; and 

 parieto-quadrate arches. Teeth pleurodont, with obtuse, compressed 

 crowns, of similar form on all the jaw-bones. Body covered with 

 osseous scuta, which are in places united by suture. Vertebrae de- 

 pressed, with simple articulations. Median, hexagonal, dermal scuta 

 on the iDarietal bone. Parietals united. 



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 inter- 

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

 lizard of the Miocene. The primary group to which it is to be referred 

 is not difficult to determine.* 



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

 fontanelle in either or their common suture.t There is a large post- 

 frontal, and the usual cranial arches are present, and the quadrato-jugal 

 absent. The frontal possesses strong lateral inferior crests, but whether 

 they underarch 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 pro- 

 duced either forward or backward 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 dental foramen 

 is small and pierces its inner face. The posterior angle of the ramus 

 is broken off. 



The characters of the premaxillary bone, fontanelle, dentition, coro- 

 noid, dentary, splenial bones, and Meckelian groove place this genus 

 out of the pale of the acrodont families. The parietals and vertebrae 

 are distinct from anything known among the geccos. There is no re- 

 semblance in essentials to the AmpJiisbmnia, so that we must look for 

 its place among the numerous pleurodont families. Here the absence 

 of the knowledge of the periotic bones and sternum somewhat em- 

 barrasses us ; but other indications are clear. The coincidence of the 

 want of parietal fontanelle with the lateral frontal plates refers us at 

 once to the Leptoglossa or Diploglossa ; a reference confirmed by the 

 simple frontal and strong cranial arches. The massive form of the sur- 

 angular bone, and reduction of the angular, at once distinguishes Felto- 

 saurus from any known family of the tribe Leptoglossa, and constitutes 

 a point of near resemblance to the Gerrhonotidce. ' This appears to be a 

 real affinity, which is further confirmed by the presence of a symmetri- 

 cal dermal scutellation on the top of tfie head. 



Referring Peltosaurus, therefore, provisionally to the Gerrhonotidw, it 



* See the author's Osteological Characters of the Scaled Reptiles, in ProceediBgs Aca- 

 demy Philadelphia, 1864, p. 224. 



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

 of the parietal. 



