298 



HISTORICAL PALEONTOLOGY. 



of both jaws are furnished with tooth-like denticulations, which 

 differ from true teeth in being actually portions of the bony 



Fig. 227. Skull of Odontopteryx toliaficiis, restored. (After Owen.) 



substance of the jaw itself, with which they are continuous, 

 and which were probably encased by extensions of the horny 

 sheath of the bill. These tooth - like processes are of two 

 cizes, the larger ones being comparable to canines ; and they 

 are all directed forwards, and have a triangular or compressed 

 conical form. From a careful consideration of all the dis- 

 covered remains of this bird, Professor Owen concludes that 

 "Odontopteryx was a warm-blooded feathered biped, with 

 Avings ; and further, that it was web-footed and a fish-eater, 

 and that in the catching of its slippery prey it was assisted by 

 this Pterosauroid armature of its jaws." Upon the whole, 

 Odontopteryx would appear to be most nearly related to the 

 family of the" Geese (Anserince) or Ducks (Anatidce) ; but the 

 extension of the bony substance of the jaws into tooth-like 

 processes is an entirely unique character, in which it stands 

 quite alone. 



The known Mammals of the Mesozoic period, as we have 

 seen, are all of small size ; and with one not unequivocal 

 exception, they appear to be referable to the or*der of the 

 Pouched Quadrupeds (Marsupials), almost the lowest group 

 of the whole class of the Mammalia. In the Eocene rocks, 

 on the other hand, numerous remains of Quadrupeds have 

 been brought to light, representing most of the great Mam- 

 malian orders now in existence upon the earth, and in many 

 cases indicating animals of very considerable dimensions. We 

 are, in fact, in a position to assert that the majority of the 

 great groups of Quadrupeds with which we are familiar at the 

 present day were already in existence in the Eocene period, 

 and that their ancient root-stocks were even in this early time 

 separated by most of the fundamental differences of structure 



