﻿CRETACEOUS FORMATIONS. 



11 



strong coracoids and their articulation with the sternum, relates, in them, to the 

 mechanism of respiration. The ossified sternal ribs, with their articulations to 

 the sides of a broad sternum, indicate a like function of the breast-bone in the 

 Pterodactyle, viz., to expand the thoracic abdominal cavity, when such plate of 

 bone, with attached but jointed sternal ribs, was pressed down by the coracoids.* 

 The superadded keel, co-extended anteriorly with the connate manubrial pro- 

 cess of the sternum of the Pterodactyle, plainly bepeaks, however, additional 

 functions ; but these might have been, as M. Von Meyer suggests, the same as 

 in the penguin, or even in the mole. And, at this point, the physiologist 

 in quest of the locomotive relations of the sternum, would pass to the 

 comparison of the humerus and other bones of the fore limb ; or, failing 

 those, to a more minute scrutiny of the texture of the breast-bone of the 

 Pterodactyle. It is almost superfluous to remark that the evidence of the 

 fore limbs had shown the Pterodactyle to have been a flying animal long before 

 anything was precisely known as to its sternum. 



The development of the interpectoral process or keel of the sternum in 

 the Pterodactyle exceeds that in any of the bat tribe ; and it may be confidently 

 concluded that the flight of the winged reptile might have been, at least, as swift 

 and of as long continuance as in the Pteropi. But, viewing the pneumaticity of 

 the bones of the Pterodactyle, and the relatively greater and more continuous 

 development of the interpectoral crest of its sternum, I am led to believe it 

 to have been a creature of more extensive, continuous, and powerful flight than is 

 now enjoyed by any bat ; and the Pterodactyles may at least have been as capable 

 of migration as the great frugivorous Chi r opt era. The structural affinities, 

 however, of the Pterodactyles to the cold-blooded air-breathers, and their analogy, 

 in wing-structure, to the bats, indicate that they might have possessed the faculty 

 of becoming torpid, and of so existing during a period when their food in a given 

 locality was not attainable.! 



* From the appearances presented by the crushed specimen of Pterodactylus Gemmingi, imbedded in a 

 slab of lithographic slate, I believe that the part of the sternum showing those articulations has been 

 accidentally separated from the rest of the fractured bone. (See Von Meyer, Tab. x, op. cit.) The estimable 

 author concludes that the marginal portion of sternum, with articulations with ossified sternal ribs, was 

 originally distinct from the body or main plate of the sternum : but the plate of the specimen he describes 

 shows fractures and some mutilation of the bones. 



f The inferences from what was previously known as to the structure of the sternum of the Ptero- 

 dactyle are thus expressed by M. H. v. Meyer, in his summary of the knowledge of the Pterosamia, in 

 1859 : " Es zeigt keinen Kiel oder Grathe, und man konnte daher glauben, dass, da die Stelle zum Ansatz 

 eines krkftigen Flugmuskels fehlt, die Pterodactyln keine guten Flieger gewesen waren. In dem Mangel 

 eines Kieles scheint indess nur cine Audeutung zu liegen, dass die Thiere keine Vogel waren. Eben so 

 wenig werden sie Wanderthiere gewesen seyn, und bedurften daher auch keines so starken Brustmuskels. 

 Das Brustbein der Fledermiiuse gleicht sogar durch die Gegenwart eines Kiels mehr dem in den Vb'geln 



