1888.] 



Scaphognathus Purdoni. 



439 



3. In birds the hinder end of the palatine and front end of the 

 pterygoid are brought into close relation with the rostrum of the 

 sphenoid. This is not the case with lizards. 



4. The orbit is rarely completed by bone in birds, and never by the 

 jugal. In lizards the orbit is surrounded by bone, and thejugal forms 

 part of it. 



5. In birds there is no prefrontal bone, while it is always present in 

 lizards. 



6. No bird has a supratemporal bar of bone, but it is always 

 developed in lizards. 



7. In lizards the paroccipital process is large and formed by the 

 opisthotic. In birds the paroccipital is small and formed by the 

 exoccipital. 



8. In birds the bones of the cranium are early ankylosed ; in lizards 

 they nearly always remain separate. 



9. Birds have the premaxillee large and united into one bone, in 

 lizards they are usually small. 



10. The ant-orbital fossa which is present in birds is only occasion- 

 ally present in lizards. 



11. In birds there is always a lower temporal bar of bone extend- 

 ing from the maxilla to the quadrate. This bar is incomplete in all 

 lizards except Sphenodon, although well developed in other reptiles. 



The skull of Scaphognathus Purdoni agrees with lizards in the first 

 seven of the above characters ; and with birds in those numbered 8, 

 9, 10. Number 11 need not be considered, as it can scarcely be re- 

 garded as distinctive. The greater importance of the first seven 

 characters makes it clear that in the structure of the skull, 8. Purdoni 

 most nearly resembles the Lacertilia. 



The brain of Scaphognathus Purdoni agrees with that of reptiles in 

 its relatively small size : while the separation of the optic lobes by the 

 cerebellum and the meeting of the latter with the cerebrum, as well 

 as the possession of a distinct flocculus, are important points in which 

 it resembles the brain of the bird. On the other hand the form of 

 the optic lobes is unlike that of any living bird. 



The brain of the American fossil bird, Hesperornis, shows a striking 

 resemblance to that of Scaphognathus Purdoni, for not only is it pro- 

 portionally smaller than in recent birds, but the relation of the cere- 

 bellum and cerebrum to the optic lobes is very similar. 



The facts above stated seem to show that the Pterosauria are 

 related to the birds in the form of the brain, and to the lizards in 

 the structure of the skull. This, however, does not constitute the 

 Pterosaurian a transitional form between birds and reptiles, in the 

 sense of the Pterosauria having been derived from reptiles, or oP the 

 birds having been derived from Pterosauria ; but rather points to 

 Aves, Pterosauria, and Peptilia having been derived from some 



2 i 2 



