396 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



verging outwards from the points where they articulate with the pro- 

 cesses of the sphenoid, to articulate by movable joints at the anterior 

 and lower angles of the quadrate bones ; anteriorly they develop hori- 

 zontal plates that articulate in front with the palatines, laterally by a 

 process that, on either side, meets the os transversum. Their upper 

 surfaces form the greater part of the floor of the orbit, while on their 

 under surfaces they present for examination on either bone a longi- 

 tudinal row of minute conical teeth, the row being double behind and 

 jjroduced anteriorly so that a few of them are found upon the pala- 

 tines beyond. The i)alatines complete the roof of the mouth distally, 

 leaving between them quite an extensive palatine Assure that ceases 

 when it meets the vomer where that bone dips down to lend its aid in 

 establishing the septum narium. A palatine starting from the oblique 

 pterygoidal articulation proceeds forwards by a rather broad horizontal 

 plate that, as it comes opposite the maxillary, throws oif an external 

 and lateral process to meet that bone and close in the "nasal aperture" 

 behind; it then turns inwards to the commencement of the palatine fis- 

 sure, to proceed by a much broader plate that bounds the nasal aperture 

 internally, and only terminates by quite an extensive articulation with 

 the maxillary laterally, and with the premaxillary and vomer anteriorly, 

 curling outwards to complete the aforesaid nasal vacuities. On either 

 side an os transversum is found; this little bone is wedged in between 

 the maxillary and jugal on its outer side, while it articulates with a 

 process coming from the palatine on its inner, thus forming quite an 

 important element in comi^leting the floor of the orbit and the base of 

 the cranium. 



The bones are arranged at the base of the cranium and roof of the 

 mouth, in nearly all lizards, so as to encircle and bound certain foramina 

 or vacuities; these have been described by Owen and named by that dis- 

 tinguished anatomist as, first, the " interpterygoidal vacuity," the largest 

 of all, a mesial, open, elliptical space in our subject bounded by the 

 pterygoids and palatines laterally, the basisphenoid behind, and con- 

 tinuous with the palatine fissure anteriorly ; the next, being parial, are 

 the "ptery go-maxillary" vacuities; these occur on either side, and are 

 bounded laterally by the maxillary and os transversum, internally by 

 the pterygoid and i)alatine ; while, finally, we have the "nasal apertures," 

 bounded on their outer sides by the maxillaries, behind and internally 

 by the palatines. In Gerrhonotus, the skull being broader, these aper- 

 tures are consequently wider; otherwise the general arrangement of the 

 bones at the base of the skull is the same. In examining the eye, we 

 discover the sclerotals to be present, as they are in Aves. They are quad- 

 rate in outline, slightly overlapping each other, and number from eight- 

 een to twenty in the average number of specimens examined. 



The rami of the lower maxilla are turned outwards, so that the alveola 

 processes are the most external ; this condition is so much increased 

 after we pass the coronoid bones that the sides of the jaw become nearly 



