Page:Quarterly Journal of the Geological Society of London, vol. 34.djvu/164

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fossils on which the above genus and species of extinct bird are propounded were discovered in the London Clay of Sheppey Island, and form part of the collection of W. H. Shrubsole, Esq., of Sheerness-on-Sea, by whom they have been kindly submitted to me, with permission to take casts of them for the Geological Department, British Museum.

They consist of parts of fractured humeri, the right and left, of the same species or individual, and include the articular head of the bone, with portions of the upper and lower parts of the shaft. They are in the usual petrified condition of the Sheppey fossils, more or less impregnated with pyrites, and, from the fractured and abraded condition of the more prominent parts of the bones, seem to have been subject to the forces of transport and rolling.

The texture of the shaft, the thinness of the compact outer bony wall, and the large size of the obviously pneumatic cavity, recall the characters of the wing-bones of the large Pterodactyles of the Cretaceous period. This leads me to refer to the 'Supplement' No. iii. to the Monograph on the Cretaceous Pterosauria (Palæontographical Society's volume, 4to, for 1860), in which descriptions and figures are given of the proximal portion of the right humerus of Pterodactylus Sedgwickii, Ow., a species about the size of a large vulture (Vultur monachus, L.), of which bird comparative views of the answerable bone and part are added in the same plate (pl. iii.).

A comparison of figs. 1-3 (Plate VI.) of the present paper with figs. 1 and 2 of the plate cited will show the difference of the Eocene fossil from the Cretaceous one; a similar comparison with figs. 6-8 of plate iii. Monogr. cit. will show the avian characters of the Sheppey specimen.

In giving the results of comparisons with the humerus in different kinds of birds, I avail myself of the same terms indicative of aspect and position as are defined in that Monograph. Proximal signifies the upper, distal the lower end of the bone as it hangs in Man. In the natural position of the humerus, as at rest, in Birds, the distal end is usually higher than the proximal one. When the palm of the hand is turned forward in the pendent arm of Man, the corresponding surface of the humerus is "palmar," the opposite surface is "anconal;" the outer side of the humerus is "radial," as being that which the radius holds; the opposite or inner side is "ulnar." The answerable surfaces or aspects bear the same names in the humerus of the bird. "Proximad," "palmad," &c. are adverbial inflexions,