coPE.l PALEONTOLOGY MIOCENE PERIOD. 513 



remains to consider the generic characters. The temporal fossa M'as 

 not roofed over by true bone, though the border of the postfrontal 

 encroaches on it; and it is rather small. The orbits, on the other hand, 

 are large, and the malar bone forms asegment of a circle. The parietal 

 thins out behind, and its posterior border has a subrouud excavation. 

 The two median dermal scuta, which left their imi)ressions on the parie- 

 tal bone, represent the interparietal and postinterparietal plates re- 

 spectively; the latter especially characteristic of the Gerrhonotidce, and 

 not found in leptogloss or diplogloss families generally ; those possess- 

 ing it being the Lacertidce in the former, and Anguidce in the latter. 

 The most prominent character which distinguishes this genus from 

 GerrJionotus is the existence of the osseous scuta which covered the 

 body. Even the form of these is similar to the corresponding dermal 

 scuta of the existing genus. 



Peltosaurus g-ranulosus, Cope, Pal. Bull., ISTo. 15, p. 5. 

 ■ Indicated by considerable i)ortious of a skeleton, which I excavated 

 from the matrix. Parietal bone broad and flat, frontal little narrowed, 

 gently convex, both with finely granular upper surface. Scuta not 

 keeled, finely granular. IsTumber of teeth on premaxillary bone, 7; 

 teeth on dentary, 10 in 0™.010. Surfaces of dentary smooth. 



Measurements. 



M. 



Median width of parietals 0.0140 



Median width of frontals .0080 



Leugth of mandibular ramus to cotylus 0400 



Diameter of vertebral centrum, (transverse) 0030 



Length of vertebral centrum 0055 



Size about that of the American Heloderma. 

 EXOSTINUS, Cope. 



Synopsis New Vert. Colorado, p. 16. 



€har. gen. — This form of lizard is represented principally by a nearly 

 entire frontal bone. Close to it were found a zygomatic bone and a 

 nearly complete dentary bone with the teeth. Tbe former is in all 

 respects appropriate 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 aifinities of this genus to Peltosaurus, Cope. 



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

 leptogloss Pleurodonta, while the olfactory lobes were almost as com- 

 pletely 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 con- 

 vex edge. They are similar in form throughout the dentary bone. 

 Cranial bones covered with symmetrical osseous prominences. 



These details, so far as they go, resemble those of Peltosaurus, and 

 Exostimis is doubtless to be referred to the same natural tribe of lizards, 

 the Diploglossa. The rugosities of the cranium indicate its greater 

 resemblance to Heloderma than to Gerrhonotus, but the teeth are much 

 more like those of the former genus than the latter. This genus and 

 Peltosaurus constitute our first definite knowledge of the extinct forms 

 of Diploglossa. 

 33 GS 



