394 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



lates tliroaghoiit its entire margin with the squamosal overlapping the 

 latter at its termination and abutting against the lateral j)rocess of the 

 occipital. In their course these wings of the parietals bend down- 

 wards by a gentle curve, which is more abrupt in the shorter skull of 

 Gerrhonottis. 



The interfrontal suture is persistent, and these bones form the mid- 

 plates at the top of the skull; taken together the plate is narrower 

 behind than it is in front, where it meets the nasals, while on either 

 side it articulates with the lacrymal and postfrontal 5 a limited portion 

 of this margin being free, it enters into the formation of the superior 

 moiety of the periphery of the orbit. In onr HolbrooMa maculata among 

 the Iguanidce we find this interorbital portion of the frontal plate 

 crowded to a mere osseous aid median line by the immense orbits. 

 The nasals have united medially just as the froutals have, and they, be- 

 ing now anteorbital, are allowed to curve downwards on either side to 

 meet the maxillaries, while anteriorly they form the upper and posterior 

 margin of either nostril, and receive between them in the middle line 

 the posterior process or nasal process of the premaxillary. This latter 

 bone forms the rounded anterior end of the skull; it also completes 

 the nostril in front and below, this subcircular aperture having its 

 border or periphery eventually made entire by the assistance of the 

 maxillary on either side, it filling in the lower and. posterior part. This 

 portion of the skull is formed in a like manner in Eumeces, but in this 

 genus the termination of the cranium anteriorly is more acute, being 

 blunter and broader in GerrJionotus scincicaudus. *We will complete 

 this view of the cranium by calling attention to the longitudinal fora- 

 men that exists anteriorly between the squamosal and parietal on either 

 side. 

 The lateral aspect of the skull (Fig. 1) presents for examination 



quite a number of interesting points. 

 We have, posteriorly, a free os quadratiim 

 that stands as a protecting pillar at the 

 portals of the auditory meatus. This 

 bone has a quadrilateral outline in front, 

 nearly flat, while behind it is deeply con- 

 cave throughout its length, and supports 

 '^'•^' ' below an oblong facet, placed transversely 



for a similar shaped articulating surface on the lower maxilla. Above 

 it is very much expanded, antero-posteriorly, the hinder part of which 

 surface is occupied by the end of the squamosal. This form of the os 

 quadratum (0. ^., Fig. 1) obtains in GerrJionotus und Uumeces, and in fact 

 seems to be but slightly departed from by the vast majority of our lizards. 

 Between the anterior boundary of the os quadratum and the posterior 

 boundary of the orbit, and the arching squamosal above that meets both 

 points, there is exposed to view in the skull of this lizard, and, I believe, 

 in all of its congeners, through an open space here existing, the delicate 



