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 
vertebree 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 
FPterodactylus itself, and these later forms are much more 
gigantic in their dimensions than their predecessors. Thus 
some of the Cretaceous Prerosaurs 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 Pferosaurs 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. Zomgiceps) 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 Decnosaurs 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 /ewanodon, so 
called from the curious resemblance of its teeth to those of the 
existing but comparatively diminutive Zgwana. 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 Zewanodon employed its teeth in actually 
chewing and triturating the vegetable matter on which it fed. 
There can therefore be no doubt but that the Zewanodon, m 
spite of its immense bulk, was an herbivorous Reptile, and 
