Nos. 455-456.] FAMILIES AND HIGHER GROUPS. 



847 



the conditions as they really occur in nature, the Class Aves is 

 susceptible of being divided into but tzvo orders, — the first or 

 Order I, including the Saurur^e, and the second, or Order II, 

 including all other bird-forms, whether extinct or existing, that 

 do not belong to Order I. This Order II is known as the 

 ORNiTHURyE. There can be no possible doubt but what in the 

 early history of birds these two orders arose from the same gen- 

 eral ancestral stock, but during the geologic ages that have fol- 

 lowed since, myriads of species have become extinct and the 

 remains of this vast host have never, save in a few isolated 

 instances, ever been found or seen by us. Hence the profundity 

 of the gap now existing between the Saururae and the Ornithurae. 

 As wide as this gap is, however, the discovery of a very few of 

 the extinct and intermediate types would tend to greatly lessen 

 its width. Nevertheless, we must classify the forms as we have 

 them, and as we find them, and to do this consistently we must 

 recognize the two orders aforesaid. 



Furbringer in his classification considers the Saururae and the 

 Ornithurae each to represent a subclass. In this I cannot agree 

 with him. Birds offer no such division, and are, as a matter of 

 fact, too homogeneous in their structure to admit of it. 



The Saururce, as is well known, are at present represented by 

 that unique, if it be unique, form Archaeopteryx of the family 

 Archaeopterygidte. There is every reason to believe that there 

 once existed higher divisional groups of this family, therefore 

 the order Saurura; is here subdivided into the supersuborder 

 Archornithiformes and the suborder Archornithes (see "A 

 Classification of Vax^^^s,'' postea). As thus created this order is 

 capable of admitting into it any other fossil genus or genera of 

 birds allied to Archaeopteryx, whether they come from the 

 Jurassic age of the Mesozoic epoch of Bavaria or from any other 

 geologic horizon in any other part of the world. So far as is at 

 present known they represent the oldest avian types in the hands 

 of science. 



The classification of birds set forth in the present memoir 

 carries the arrangement down to include the families only, while 

 for the higher groups, intermediate between the order and the 

 family, I employ the superfamily, the suborder and the super- 



