xi THE GEOLOGICAL RECORD 211 



Fragments of bones from the English Chalk indicate an 

 equally large size. The backward prolongation of the head 

 is supposed to show that the powerful muscles required 

 for such immense wings were attached to the head. This is 

 rendered more probable by the skull, nearly 4 feet long, of 

 another still larger species, in which the occipital crest pro- 

 jects a foot back from the head, and which Professor Marsh 

 believes had a spread of wing of 20 or even 25 feet (Fig. 66). 



FIG. 66. LATERAL VIEW OF SKULL OF PTERANODON LONGICEPS. 

 From the Cretaceous of North America. One-twelfth nat. size. The jaws are 

 entirely without teeth. There is an enormous occipital crest (c ) projecting far 

 behind the occiput, to which the muscles for flight were probably attached ; 

 (a) the nares and pre-orbital cavity ; (6) the orbit. This species had an 

 expanse of wings of about 20 feet. (From Nicholson's Manual of 

 Palaeontology. ) 



We thus see that during the Secondary epoch the great 

 class Reptilia, which had originated apparently during the 

 last stages of the Primary, became developed into many 

 special types, adapted to the varied modes of life which 

 the higher warm-blooded vertebrates have attained in our 

 own time. The purely terrestrial type had their herbivora 

 and carnivora corresponding to ours in structure and habits, 

 but surpassing them in size ; the amphibious or marsh 

 species surpassed our largest existing crocodiles, while the 

 true aquatics almost exactly anticipated the form and habits of 

 our porpoises and smaller whales. The air, too, was peopled 

 by the strange Pterodactyls which surpassed the bats in 

 powers of flight, in which they almost rivalled the birds, 

 while they exceeded both in the enormous size they attained. 

 Considering how rare must have been the circumstances 

 which led to the preservation in the rocks of these aerial 

 creatures, we may conclude, from the large number of 

 species known to us, that they must have been extremely 

 abundant in middle and late Mesozoic times, and that 



