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22 previously considered to be a femur, he found that it was really the distal end of the tibia, corresponding in all its broad features with Cuvier's specimen from the Honfleur clays. Deslongchamps's very just appreciation of the close affinity between his Poikilopleuron and Megalosaurus would have been immensely fortified if he had been acquainted with the true structure of the distal end of the tibia of the latter reptile.

I had got thus far in February 1868, and it was on the strength of the facts just mentioned that I included Poikilopleuron in the list of the Dinosauria, in the lecture which has been cited. At that time, however, I had not seen the following notes by Prof. E. D. Cope, of Philadelphia, which are contained in the 'Proceedings of the Academy of Natural Sciences of Philadelphia,' for November 1866 and December 1867, and in the 'Proceedings of the Boston Natural History Society' for June 1869, and which constitute important additions to his previously published account of the American Megalosauroid Lælaps.

The similarity of Prof. Cope's general conclusions to my own, in his second note, render it necessary for me to point out that I could not possibly have known anything about them when my lecture was delivered, still less at the time when the letter from Prof. Phillips which I have cited, was written.

"E. D. Cope pointed out the anomalous relations existing between the tibia and the fibula in certain of the Dinosauria, as illustrated by the genus Lælaps. He remarked, the distal extremity of the tibia is transverse and much compressed, and does not exhibit any of the usual appearances of an articular surface, neither the reptilian condyle, nor a cotyloid cavity sufficient for an astragalus of the size necessary for an animal of such bulk. A bone presenting a broad hour-glass-faced articular surface was discovered with the other remains, and had puzzled the anatomists who had seen it. This piece exhibits along its whole posterior aspect two faces, which form a reentrant angle for a fixed articulation; this is found to have been applied to the extremity of the tibia exactly, and to have been fixed by strong articular ligaments. The medianly constricted condyle, presenting forwards and a little downwards, exhibits so little analogy with the astragalus, as to suggest other interpretations; and after a careful examination, it seeing evidently the distal extremity of the fibula. This element furnishes a small articular surface at the knee, and fitting the tibia by the concavity of its inner face, becomes greatly attenuated at its distal third, where it is, in consequence of the obliquity of its direction, applied to the anterior face of the former bone. It then spreads into a plate extending to the inner margin of the tibia, while the solid shank is continued along the outer margin, and both terminate in the massive condyle, which embraces the whole extremity of the tibia, like an epiphysis.

"One other example only of this structure is known in the Vertebrata, of which I only find mention in Cuvier, 'Ossemens Fossiles,'