THE CRETACEOUS PERIOD. 277 



long tail of the Ichthyosaur with the long neck of the Plesio- 

 saur. The length of this monstrous Reptile could not have 

 been less than fifty feet, the neck consisting of over sixty 

 vertebrae and measuring over twenty feet in length. The 

 extraordinary Flying Reptiles of the Jurassic are likewise well 

 represented in the Cretaceous rocks by species of the genus 

 Pterodactylus itself, and these later forms are much more 

 gigantic in their dimensions than their predecessors. Thus 

 some of the Cretaceous Pterosaurs seem to have had a spread 

 of wing of from twenty to twenty-five feet, more than realising 

 the " Dragons" of fable in point of size. The most remark- 

 able, however, of the Cretaceous Pterosaurs are the forms 

 which have recently been described by Professor Marsh under 

 the generic title of Pteranodon. In these singular forms so 

 far only known as American the animal possessed a skeleton 

 in all respects similar to that of the typical Pterodactyles, 

 except that the jaws are completely destitute of teeth. There 

 is, therefore, the strongest probability that the jaws were 

 encased in a horny sheath, thus coming to resemble the beak 

 of a Bird. Some of the recognised species of Pteranodon are 

 very small ; but the skull of one species (P. longiceps) is not 

 less than a yard in length, and there are portions of the skull 

 of another species which would indicate a length of four feet 

 for the cranium. These measurements would point to dimen- 

 sions larger than those of any other known Pterosaurs. 



The great Mesozoic order of the Deinosaurs is largely rep- 

 resented in the Cretaceous rocks, partly by genera which 

 previously existed in the Jurassic period, and partly by entirely 

 new types. The great delta-deposit of the Wealden, in the 

 Old World, has yielded the remains of various, of these huge 

 terrestrial Reptiles, and very many others have been found in 

 the Cretaceous deposits of North America. One of the most 

 celebrated of the -Cretaceous Deinosaurs is the Iguanodon, so 

 called from the curious resemblance of its teeth to those of the 

 existing but comparatively diminutive Iguana. The teeth (fig. 

 209) are soldered to the inner face of the jaw, instead of being 

 sunk in distinct sockets; and they have the form of somewhat 

 flattened prisms, longitudinally ridged on the outer surface, 

 with an obtusely triangular crown, and having the enamel 

 crenated on one or both sides. They present the extraordinary 

 / feature that the crowns became worn down flat by mastication, 

 showing that the Iguanodon employed its teeth in actually 

 chewing and triturating the vegetable matter on which it fed. 

 There can therefore be no doubt but that the Iguanodon, in 

 spite of its immense bulk, was an herbivorous Reptile, and 



