1856.] OWEN — GASTORNIS PARISIENSIS. 213 



Comparison. — Having premised the foregoing remarks on the 

 modifications of the distal end of the tibia in some existing examples 

 of every order of birds, I proceed to apply this knowledge to the 

 elucidation of the nature of the fossil tibia of the Gastornis dis- 

 covered in the lowest eocene beds in the vicinity of Paris. 



In this fossil, fig. 1, the distal end is much mutilated : the anterior 

 projecting convexities of both condyles are broken away, and both 

 the under and posterior trochlear surfaces are to a certain extent 

 wanting : a small tract of the original smooth articular surface remains 

 there, and a smaller portion is left on the broken outer condyle. 

 The proportion of breadth to depth of this end of the bone is, 

 therefore, indeterminable in the sole example discovered. It would 

 seem as if the anterior intercondyloid or supercondyloid surface had 

 been divided from the articular surface by as abrupt a transverse bar 

 as in the Ostrich, Dinornis, and certain GrallcB ; and the under sur- 

 face appears to have had a similar extent and contour of surface to 

 that in the GruidcB : it seems to have been broader and flatter than 

 in the Dinornis. Posteriorly the trochlea is relatively as broad as in 

 the Gallince, and is broader than in the Grallce. The rough frac- 

 tured base of the inner condyle shows that the intercondyloid space 

 was relatively narrower than in the Anatidce, and most other water- 

 birds. The supratendinal bridge is more median in position than in 

 most of the Grallce ; though not more so than in the Gallinule and 

 Oyster-catcher. This median position, though common in the Nata- 

 toreSy is not peculiar to them. The Curlew, Notornis, Raven, Eagle, 

 and the Crown Pigeon have a similar position of the bridge. 



The direction of the bridge appears to have been nearly transverse ; 

 but much of it is broken away. The canal leading to it is bounded by 

 a well-marked ridge internally, but seems to want an outer boundary : 

 the aspect of the lower opening is obliquely forwards and downwards, 

 as in the Gallince and some Grallce; not directly forwards, as in 

 most Natatores. As to the distance of that opening from the lower 

 surface of the trochlea, it is not relatively greater than in the Turkey, 

 the Cock, the Gallinule, and the Anatidce. The depression beneath 

 that outlet in the fossil, if it be natural, is a peculiarity I do not find 

 in any Wading-bird. The depression above the articular trochlear 

 surface in the Bustard, e.^.,is one into which the tendinous canal opens, 

 and is chiefly due to the transverse ridge developed from the bridge 

 spanning the canal. In the Argala it is due to the strong tubercle 

 similarly developed above the outlet of the canal ; in the Grus to a 

 similar tubercle projecting forwards external to the outlet. 



The Curlew (Numenius arcuata, fig. 15) and Oyster-catcher 

 (Hcematopus) show a more shallow depression below the outlet. 

 The smooth surface of the middle of the depression on the outer side 

 of the condyle appears to indicate its concavity, but the border is too 

 much broken away to enable one to judge of its original depth. 



The relative breadth of the posterior part of the trochlear surface 

 agrees with that in the Turkey and the Swan ; but the borders are 

 here, also, too much broken away to enable one to determine its 



