WINGED REPTILES. 321 



two inches in diameter; and this hollowness extended into nearly 

 every bone of the skeleton, from the toes to the ribs and the slcull. 

 Moreover, the bones were all of fine and firm texture, and the sutures 

 or immovable joints throughout the body were fused or anchylosed, as 

 is the case with birds, thus giving the maximum of strength with the 

 minimum of weight. The larger bones had each one or two pneumatic 

 openings in them, through which doubtless entered ramifications of 

 the bronchial tubes, as in birds. 



Altogether the weight of a Pteranodon of the largest size in life 

 could scarcely have reached twenty-five pounds — the bones of the 

 skeleton having an expanse of twenty feet, even as petrified, do not 

 weigh more than five or six pounds. This extreme lightness, together 

 with the vast expansion of the volant membranes, suggests as a com- 

 parison the hull and sails of a Columbia or Shamrock. With the per- 

 fect and delicate construction and their strong articulations, the fusion 

 of all loose bones, the presence of sclerotic plates in the eyes giving 

 greater control over vision in high altitudes and in the dark, the pos- 

 session of a relatively large and bird-like brain, all conclusively demon- 

 strate the flight powers of these singular reptiles. 



Upon land even the best of the pterodactyls must have been awk- 

 ward and ungainly, creeping about upon hands and feet, impeded by 

 the cumbersome head and flapping membranes. It is doubtful, indeed, 

 whether the more highly specialized forms like Pteranodon often 

 voluntarily sought the surface of the ground; they doubtless spent the 

 most of the time while not flying, suspended from cliffs and trees by 

 means of their slender, clawed fingers. In the air they reigned supreme 

 and alone, save for the small toothed birds which were then making 

 their appearance in geological history, and which may often have 

 served as delicious tid-bits for their insatiable maws. The sharp, 

 dagger-like beak, driven by the powerful neck, was certainly a murder- 

 ous weapon against their enemies, whether upon land or in the air. 

 That they laid eggs, like most reptiles, is almost certain. Did they 

 build nests in inaccessible heights? 



That the ornithosaurs for a long time enjoyed a wide distribution 

 throughout the world is certain — their remains have been discovered in 

 the most remote parts of the earth, and wherever the conditions were 

 favorable for their existence and the rocks for the represervation of 

 their remains, traces of them may be confidently expected to be found. 

 In ISTorth America, with a single exception, their fossilized bones have 

 been discovered only in the Cretaceous deposits of western Kansas. 

 Throughout this region there are wide exposures of pure chalk, the 

 sediment of the old Cretaceous ocean, which at one time extended 

 from the Gulf of Mexico to the Arctic Ocean, and from central Kan- 

 sas on the east to far into Colorado on the west. Because of the pro- 



VOL. LX. — 21. 



