LAOEETILIA. 775 



M. 



Length of mandibular ramus to cotylus .0400 



Diameter of vertebral centrum (transverse) 0030 



Length of vertebral centrum 0055 



Length of a dorsal scutum 0075 



Width of a dorsal scutum 0042 



About the size of the Heloderma suspedum. 



EXOSTINUS Cope. 



Synopsis of New Vertebrata Colorado, 1873, p. IG. Annual Report U. S. Geol. Surv. Terrs., 1873 (1874), 



p. 511. 



This form of lizard is represented principally by a nearly entire 

 frontal bone. Close to it were found a zygomatic bone and a nearly com- 

 plete dentary bone, with the teeth. The former is in all respects appro- 

 priate to the frontal bone, and the size of the dentary bears the usual relation 

 of size to the same. Its dentition is appropriate to the affinities of this 

 genus to Peltosaunis Cope. 



The frontal bone is much narrowed between the orbits, as in recent 

 leptogloss Pleurodonta, while the olfactory lobes were almost as completely 

 underarched as in the thecagloss-type. The stout, well-developed zygomatic, 

 with malar process, resembles the former group, and the teeth have a similar 

 structure. These are closely placed, truly pleurodont and subcylindric. 

 The crowns are simple, compressed, and with a convex edge. They are 

 similar in form throughout the dentary bone. Cranial bones covered with • 

 symmetrical osseous prominences. 



The sculpture of the superior surface of the frontal bone is more like 

 that of the genus Anolis than any other known to me. The prominent 

 inferior lateral olfactory crests, are, however, entirely inconsistent with any 

 such affinity, excluding the genus from the Iguanian group altogether. It 

 coincides with the evidence furnished by the forms of the teeth, that the 

 genus Exosthms is one of the Diploglossa^ and allied, but not very closely, to 

 Peltosaurus. In the latter the frontal region is much wider, and is not 

 covered with tubercles, and the olfactory ridges are much less prominent. 

 In its narrow interorbital region Exostinus differs from any recent genus of 

 the order known to me. 



