19 



fortunately represented by more than a single specimen, 

 clearly indicates a much higher antiquity for the class. The 

 earliest American forms, at present known, are the Odontornithes, 

 or Birds with teeth, which have been exhumed within the last 

 few years, from the Chalk of Kansas. The two genera, Hes- 

 peroimis and Jchthyornis, are types of distinct orders, and differ 

 from each other and from Archceopteryx much more than do 

 any existing birds among themselves; thus showing that Birds 

 are now a closed type, and that the key to the history of the 

 class must be sought for in the distant past. 



In Hesperornis, we have a large aquatic bird, nearly six feet 

 in length, with a strange combination of characters. The jaws 

 are provided with teeth, set in grooves; the wings were rudi- 

 mentary, and useless ; while the legs were very similar to those 

 of modern diving birds. This last feature was merely an adap- 

 tation, as the more important characters are Struthious, showing 

 that Hesperornis was essentially a carnivorous swimming Ostrich. 

 Ichthyornis, a small flying bird, was stranger still, as the teeth 

 were in sockets; and the vertebrae biconcave, as in Fishes, 

 and a few Reptiles. Apatornis and other allied forms occur 

 in the same beds, and probably all were provided with teeth. 

 It is strange that the companions of these ancient toothed 

 Birds should have been Pterodactyls without teeth. In the 

 later Cretaceous beds of the Atlantic Coast, various remains 

 of aquatic Birds have been found, but all are apparently dis- 

 tinct from those of the West. The known genera of Ameri- 

 can Cretaceous birds are, Ajjatorjiis, Baptornis, Gracu/avns^ 

 Hesperornis, Ichthyornis, Laornis, Leslornis, Pakeotringa and 

 Telmatornis. These are represented by some twenty species. 

 In Europe, but two species of Cretaceous birds are known, 

 and l)oth are based upon fragmentary specimens. 



During the Tertiary period. Birds were numerous in this 

 country, and all yet discovered appear to have belonged to 

 modern types. The Eocene species described are mostly wading 

 birds, but here, and in the later Tertiary deposits, some charac- 

 teristic American forms make their appearance, strongly fore- 



