1883.] NATURAL SCIENCES OF PHILADELPHIA. 101 



jugal is rather small. Its articulation with the quadrate is 

 squamosal. The maxillary is convex on its outer face, presenting 

 the teeth inwards. The nasals are distinct, and much narrowed 

 forwards to their junction with the spines of the premaxillaries. 

 The latter bones are distinct. They form, when viewed from 

 above, an anchor-shaped bodv, with the curved flanges extending 

 outwards and backwards. These enclose, with the anterior apex 

 of the maxillaries, the huge external uareal orifices, which were 

 probably roofed over by membrane, as in the birds. 



The pterygoids extend well posteriorly as broad plates, and are 

 in close contact with the inferior part of the quadrates. They are 

 separated for a short distance on the middle line posteriorly by a 

 fissure, which, with the narrow space between the pterygoids and 

 the presphenoids, gives exit to the transversely narrowed posterior 

 nares. The occipital condyle looks downwards. The sphenoid is 

 posteriorly horizontal, and overlaps the basioccipital with only a 

 trace of lateral tuberosities ; but in front it is curved abruptly 

 downwards. At this point, an elongate, flattened, truncate process 

 extends posteriorlj'^, forming the median part of the roof of the 

 fissure of the posterior nares. In front of this fissure the pter}"^- 

 goids are in contact, and extend a considerable distance ante- 

 riorly ; at least to opposite to the border of the large anterior 

 palatomaxillary foramen. 



The maxillary bone is produced far posteriorly, so as to define 

 the zygomatic foramen on the inner side. The palatine bone 

 extends posteriorly between it and the pterygoid for a considerable 

 distance, when the expanding pterygoid cuts it off, and extends 

 to the posterior extremity of the maxillary, closing the space 

 occupied in the Lacertilia by the posterior palatomaxillary foramen. 

 I cannot distinguish whether the portion which extends to the 

 maxillary bone is distinguished as an ectopterygoid. The posterior 

 edge of this part of the pterj'goid projects below the posterior part 

 of the bone, which is nearly horizontal until it reaches the quad- 

 rat^. It then ascends, forming a lamina on the inner side of that 

 bone, reaching the process from the inner side of the condyle. 



The vomer is a narrowed, horizontal lamina between the anterior 

 parts of the maxillary bones, anterior to which point it does not 

 appear to extend. It soon becomes a vertical lamina, spreading 

 at the base, where it is in contact with the middle line of contact 

 of the pterygoid bones (and perhaps of the palatines, but these 



