THE FOSSIL AVIFAUNA OF THE 
419 
In determining this species I compared its fossil bones most carefully with the 
corresponding ones in skeletons of representatives of the genera Sialia, Hespe- 
roachla, Mertila, Turdus, Myadestes, Campylorhyncims, Harporhynchns, Miuius, 
Oroscoptes, Laniiis, Ampelis, all our large conirostral species, western and other- 
wise ; all the medium sized I cte7'tdce ; Otocorts ; and specimens of the species of 
western Tyranmda. It agrees alone, in all characters, with the genus in which I 
have placed it. My own cabinet afforded the above material. (St'e Kiff 10 
PI. XV). 
Specimens of fossils all in Professor Coj^e’s collection : Erpins Beds, Silver Lake 
Region, Oregon. 
CoEVUS ANNECTENS Sp. nov. 
Recognized through the discovery of a right tarso-metatarsns, j)erfect with the 
exception of the loss of the inner articular facet at the summit. Having exactly 
the same characters as the corresponding bone from a skeleton of Corvus corax 
sinuatus, it nevertheless belonged to a species a full size smaller. Havens of the 
present day vary much in size, the smaller forms being found in the .southwestern 
parts of the United States, and the largest specimens in Alaska, while Ixdween these 
two limits the intermediate sizes gradually approach each other. 'Die skeleton 
I have for comparison in the joresent instance is from a female I shot in New .Mexico, 
and probably represents the minimum size of the modern bird ; Cor~i>tts anncctcns is 
very perceptibly smaller than it, as may be seen by the following measurements irj 
millimetres. 
Length of tarso-metatarsus 
Transverse diameter, mid-shaft 
C. c. sinuatiis. t’. 
04 
aiinccteiiH. 
01 
4 
Transverse diameter, trochlear end <) g 
Height of hypotarsus 4 
In the absence of other material it would appear that the simillest .\merican 
Ravens are the extinct forms, and that the species has increased in size since the 
Pliocene epoch, especially the boreal branch of the original stock. The gradation 
appears to be almost perfect, yet it would seem that between the pi'csent extinct 
species, and the largest Alaskan forms, there exist good specific difterences. (8c*e 
Figs. 14, 15 and 16, PI. XV). 
Cope collection : Pliocene of Oregon. 
CONCLUSIONS. 
To briefly recapitulate the events in the geological history of the continent 
west of the Mississippi River that led up to the epoch which has engaged our 
attention in the present memoir, it will be remembered that during the cretaceous 
times a great, shallow sea of broad expanse covered the entire central jiart of the 
55 JOUR. A. N. S. PHILA., VOL. XI. 
