2i2 PALEONTOLOGY 



of the muzzle. The very narrow cranium, wide temporal fossa? 

 on each side, bounded posteriorly by the parietal and the 

 mastoid bones, and laterally by strong compressed zygomata ; 

 the long tympanic pedicle, descending freely and vertically 

 from the point of union of the posterior transverse and zygo- 

 matic arches, and terminating in a convex pulley for the 

 articular concavity of the lower jaw ; the large and complete 

 orbits, and the short, compressed, and bent down maxilla?, all 

 combine to prove the fossil to belong to the lacertian division 

 of the saurian order. The mode of articulation of the skull 

 with the spine cannot be determined in the present specimen, 

 but the lateral compression and the depth of the skull, the 

 great vertical breadth of the superior maxillary bone, the 

 small relative size of the temporal spaces, the vertical breadth 

 of the lower jaw, prove that it does not belong to a reptile of 

 the batrachian order. The shortness of the muzzle, and its 

 compressed form, equally remove it from the Crocodilians. No 

 Chelonian has the tympanic pedicle so long, so narrow, or so 

 freely suspended to the posterior and lateral angles of the 

 cranium. 



The general aspect of the skull differs, however, from that 

 of existing Lacertians, and resembles that of a bird or turtle, 

 which resemblance is increased by the apparent absence of 

 teeth. The dense structure of the produced ends of the pre- 

 maxillaries indicates an analogy of function to the tusks of 

 Dicynodon ; the premaxillaries are double, as in crocodiles and 

 Chelonians ; but most of the essential characters of the skull 

 arc those of the lizard. The rami of the lower jaw are remark- 

 able, as in Bathygnathus, for their great depth, but not the 

 least trace of a tooth is discernible in the alveolar border of 

 the dentaiy element. 



The cranium, in my first described Rhynchosaur, was pre- 

 served with the mouth in the naturally closed state, and the 

 upj>er and lower jaws in close contact. In this state we must 



