80 ME. C. W. ANDEEWS ON THE SKULL AND 



the lower end forms the inner border of the very deep groove for the extensor tendons ; 

 it terminates at the inner end of the extensor bridge. This latter lies obliquely ; near 

 the upper border of its inner end there is a deep pit for the attachment of the oblique 

 lio-amentous sling through which the tendon of the tibialis anticus passes : the other 

 end of the ligament is inserted lower down on a well-marked tubercle just above the 

 outer condyle ; the lower border of the bridge passes externally into a prominent 

 tuberosity, such as occurs in the Storks, &c, and serves for the insertion of the ligament 

 bridging the extensor tendons. 



The condyles are about equal in size, and are separated by a deep intercondylar gorge 

 which opens above into a median concavity lying in the middle line immediately below 

 the last-mentioned tuberosity, and, when the leg is flexed, receiving the large inter- 

 condylar tuberosity of the metatarsus. Posteriorly the intercondylar groove is short and 

 shallow, but is still sharply defined, being bounded by the prominent posterior projections 

 of the condyles. Looked at from the side the outer condyle is nearly circular in 

 outline, while the inner is much elongated from before backward ; both are concave 

 on their outer surfaces. 



The upper end of the bone is relatively small, but the pro- and ectocnemial crests 

 are fairly well developed and rise considerably above the proximal articular surface, 

 which slopes upward and forward. The inner glenoid surface is flat or only 

 slightly convex ; posteriorly it forms a considerable projection and is separated by 

 a notch from the outer or fibular surface, which is small and very convex in all 

 directions. 



There are no pneumatic foramina. The centre of the shaft is occupied by a large 

 smooth-walled cavity, and the thickness of the bone in the middle of the shaft does 

 not exceed 4 mm. 



The tibio-tarsus of Diomeclea differs from that of the fossil in the much greater 

 breadth of the intercondylar fossa, the nearly transverse direction of the extensor 

 bridge and the absence of a tuberosity at its outer end, and in possessing a much 

 larger cnemial crest. 



In Grus the tibia differs widely in the relatively greater width of the distal 

 articulation, in which the condyles are small and the intercondylar groove broad ; on 

 the other hand, there is a median tuberosity. 



In Psophia the extensor bridge is much more transverse, and the outer condyle 

 considerably the larger, as in Rails. 



In Cariama the condyles are relatively smaller and the intercondylar groove 

 shallower and broader. 



In Ciconia the tibia presents considerable resemblance to the fossil, but the 

 articular surfaces for the femur are less distinctly separated, the extensor bridge is 

 less oblique, and the groove for the tendons occupies the whole width of the shaft. 



In the Accipitrine birds, including Serpentarius, the cnemial crests are very small, 



