PKOE. OWEN ON THE SETTLE OP MEGALOSATJEUS. 343 



including the two sacrals and two others, which are probably refer- 

 able to the lumbar and caudal vertebrae" *. 



Baron Cuvier, incorporating Buekland's discovery in the con- 

 cluding volume of his ' Ossemens Fossiles,' refers to the figure cited 

 below as " Suite de cinq vertebres de Megalosaurus"t, without 

 further definition. 



In determining the nature and class of these five coalesced ver- 

 tebras as truly "sacral" — and that determination has been accepted — 

 I did not indicate, as has been alleged, any affinity therefore to the 

 class Mammalia, but proceeded to unravel the structure of the 

 sacrum, and demonstrated that it was such as occurred in no 

 Mammal, but was repeated in the class of Birds. 



Now, the condition to which I have referred, which has deceived 

 such able palaeontological osteologists as Yon Meyer and Huxley in 

 regard to the construction of the upper jaw in Birds and Ptero- 

 dactyles, and by inference in Megalosaurs, the speedy confluence, 

 viz., of essentially distinct bones and bony elements in Birds, 

 constituted the main difficulty to be overcome in the correlation 

 of the peculiar and, at that time, unique structure of the sacrum of 

 the Megalosaur with that of the many-vertebrated sacrum in other 

 classes. 



In the extinct reptile the neurapophyses, in each vertebra, were 

 shifted in position from their proper centrum so as to cross the 

 interspace of two centrums ; and I had to determine to which 

 of these centrums the neural arch did properly belong. The 

 mammalian class was exhausted without result ; the avian class 

 presented the difficulty of the complete blending of the several 

 sacral vertebrae with other pelvic elements into a single mass of 

 bone. 



The resource (fossils of great wingless birds not having then come 

 under my ken) was investigation of the development of the sacrum 

 of a bird ; and that line of research was not abandoned until I could 

 testify with certainty to that class of vertebrates repeating the 

 singular modification in the great terrestrial extinct ReptiliaX, thence 

 and thereupon associated together as Dinosauria. 



No other affinity is deduced from the discovery save of the Dino- 

 saur to the Bird. The result of the embryonal researches is limited 

 in the ' Report ' § to that inference. The labours leading thereto 

 are detailed in the work ' On the Archetype of the Vertebrate 

 Skeleton" ||. 



In my Hunterian Lectures at the Eoyal College of Surgeons ^[, 

 after defining the class-characters based on the circulating and 

 respiratory systems, I took occasion to remark : — " But many im- 



* Geol. Trans. 2nd Series, vol. i. (1824) p. 395, pi. xliii. fig. 1. 



t Tome v. 2 de partie (1822), p. 348. 



$ " Report on British Fossil Reptiles," Part ii. ' Reports of the British 

 Association for the advancement of Science,' vol. for 1841, pp. 105-108. 



§ Tb. ib.' 



|| 8vo, 1848, " Composition of the Sacrum in Birds," in which the congeries 

 of vertebras in that of an immature Ostrich is the subject of figure 27, p. 159. 



^[ Anatomy of Vertebrates, vol. i. 1866, pp. 6 & 7. 



2c2 



