AVES. 



47 



allelism existing between the monodelphs and didelphs. The original of this fine 



specimen is in the British Museum. A part of the right lower ramus is wanting. 



Size, 3 ft. 5 in. x 1 ft. 10 in. Price, mounted. $40.00. 



No. 182. Nototherium Mitchelli, Owen. 



Skull and Lower Jaw. This 

 quadruped, which probably rivalled the 

 Ehinoceros in size, manifests pachyder- 

 mal modifications of the marsupial type. 

 It differs from the Diprotodon in the 

 polished surface of the enamel as con- 

 trasted with the punctate surface of the 

 teeth of the latter, by the obliquity of 

 the molar ridges, and by procumbent 

 incisors of less relative size. There were 

 three molars and two premolars in each 

 ramus. From the great width of the 

 zygomatic arches, it was formerly called 

 Zygomaturus. This specimen, discover- 

 ed in the alluvial deposits near the Condamine River, Australia, is in the Brit- 

 ish Museum. Size, 20 x 18. Price, mounted, $12.00. 



No. 183. Thylacoleo carnifex, Owen. 



Lower Jaw, right ramus. This marsupial carnivore was about the size 

 of the Lion. The fossil was found in the Pleistocene formation of Australia, and 



is preserved in the British Museum. 



Price, $0.60. 



CLASS II — AVES. 



The earliest evidences of Birds are footprints on the tidal shore of 

 the Liassic Sea. The fossil bones are much more rare than those of 

 other Vertebrates, excepting, perhaps, in the favored locality of New 

 Zealand. " The powers of flight possessed by most Birds (says Lyell) 

 would ensure them against perishing by numerous casualties to which 

 quadrupeds are exposed during floods." The length of time, also, 

 during which the carcase of a Bird may float, exposes it the more to be 

 devoured, and also to the wider dispersion of its remains. The greatest 

 part of ornithic remains yet found are those of land Birds. 



Certain cylindrical bones from the Stonesfield Oolite, Wealden, and 

 Chalk have turned out under the critical eye of Owen to be Pterodac- 

 tylian. The oldest authentic ornitholites are the relics of a small Vul- 

 ture (Lithomis vulturinus) found in the Eocene clay of the Isle of 



