488 PYTHONOMORPHA CHAP. 



The nostrils are dorsal, bordered by the premaxillae, nasals, pre- 

 f rentals, and maxillaries. The quadrato-jugal arch is incomplete, 

 and the orbit is * posteriorly confluent with the infra temporal 

 fossa, but a supratemporal space is shut off by the single arch, 

 which is composed of the postfrontal, squamosal, and supra- 

 temporal. The latter is interposed between, and connects the 

 squamosal and quadrate with the latero-posterior branch of the 

 parietal. There is a space between this parieto-squamosal arcade 

 and the epi-otic, which is fused with the lateral wing of the 

 lateral occipital bone. The foramen magnum is bordered by the 

 two supra-occipital, lateral occipital, and the unpaired basi- 

 occipital bones ; the condyle is triple. The quadrate is movable, 

 articulating with the squamosal and laterally expanded epi-otic. 

 There is no bony connexion of the quadrate with the jugal, which 

 is restricted to its anterior half, and attached to the maxillary 

 and lacrymal. The quadrato-jugal is absent as a separate bone ; 

 it is probably fused with the anterior surface of the quadrate, as 

 indicated by a perforation of the quadrate, resembling in this 

 respect the Ehynchocephalia. The vomers are long, and separate 

 the elongated choanae from each other. The palatines separate 

 the vomers from the pterygoids, which enclose a long median 

 vacuity and are not connected with the quadrates. The teeth 

 are conical, and stand near the inner margin of the jaws upon 

 little prominences, with which they fuse. Some genera have 

 teeth upon the pterygoids also. 



The vertebrae are very numerous and are mostly procoelous. 

 They are noteworthy for the possession of an additional anterior 

 and a posterior pair of articulating processes on the neural 

 arches, homologous with the zygosphenes and zygantra of 

 Snakes and Iguanidae (see p. 582). Intercentra are absent, 

 except in the tail. The ribs have no tubercula, and articulate 

 with the centra of the vertebrae to which they belong. 



The pectoral arch is strong. The scapulae are short and broad ; 

 the coracoids, fused with the precoracoids, except for a notch, 

 are flat and broad, and meet ventrally ; posteriorly they articulate 

 upon the anterior margin of the flat sternum, to the lateral 

 margin of which are attached several ribs. Clavicles and inter- 

 clavicle seem to be absent. Abdominal ribs are likewise absent. 

 The pelvic girdle is feeble ; the ilia, ischia, and pubes are 

 loosely connected with each other, the pairs of ventral elements 



