ART. 5. FOSSIL BIRDS FROM ARIZONA WETMORE. 17 



roughly rounded in outline, flattened slightly from above down- 

 ward, with the external margin raised slightly so that the external 

 face is concave; posterior proximal margin deflected inward in a 

 direct slope to merge with the shaft ; anterior proximal margin pro- 

 jected farther beyond level of shaft than posterior ; internal ligamen- 

 tary tubercle elevated as a low flattened cone with lower margin 

 above center of outer face of condyle, placed in a line with the 

 anterior margin of the shaft; outer condyle nearly on a plane with 

 the outer face of the shaft, with the anterior margin thickened, 

 rounding into intercondylar sulcus ; posterior margin becoming thin 

 and swinging in to merge with the shaft at the same level as that 

 from the internal condyle ; outline of external condyle roughly ellip- 

 tical, with a raised margin all around so that the external face of 

 the bone is concave; a very slight almost inperceptible eminence 

 slightly above center; shaft in cross-section elliptical near center, 

 rounded on posterior side, becoming flattened as it proceeds down- 

 ward on anterior face; distal end somewhat expanded, distinctly 

 flattened on anterior side; supratendinal bridge (above extensor digi- 

 torum communis) moderately broad, passing obliquely from a point 

 slightly external to center of shaft to an elevated inner prominence 

 on the antero-internal end of the shaft above the outer condyle; a 

 distinct sulcus on outer anterior angle for the passage of the peroneus 

 longus; margins of this sulcus raised as distinct crests, the external 

 one being more acute than the inner one; the sulcus passing at a 

 slight angle outward; a linea aspera marking the peroneal muscle 

 passing upward from outer of these crests for a distance of 15 milli- 

 meters ; on inner anterior margin of shaft a linea aspera that marks 

 the extensor digitorum muscle, this line forming the point of junc- 

 tion of inner and anterior faces of shaft; this line terminates in a 

 thin raised crest for the attachment of the inner end of the oblique 

 ligament (below which passes the tendon of the tibialis anticus) ; 

 external tubercle for oblique tendon a crest above upper external 

 margin of the tendinal bridge for the extensor digitorum communis. 



Measurements of the specimen are as follows: Condylar breadth, 

 9.4 mm.; transverse diameter of shaft near center (of complete 

 specimen), 4.5 mm.; transverse diameter of internal condyle, 8.7 

 mm. ; transverse diameter of external condyle, 7.6 mm. ; distance from 

 center of tubercle for internal ligament to lower margin of internal 

 condyle, 5 mm. 



In the genus Corvus the lower end of the tibio-tarsus in the ravens 

 is distinguished by the prominent high, sharp crest that extends 

 well up on the inner side of the shaft, with the groove for the 

 'peroneus profundus relatively broader and placed at a higher eleva- 

 tion. In this Corvus cryptole.ucns agrees with C. corax. The crows, 

 on the contrary {G. hrachyrhynchos and C. ossifragus), have the 



