124 .PROP. OWEN ON AEGILLOENTS LONGIPENNIS. 



10. On Aegilloenis* longipennls, Ow., a large Bied of plight, 

 from the Eocene Clay of Sheppey. By Prof. Owen, C.B., 

 E.R.S., F.G.S., &o. (Read December 19th, 1877.) 



[Plate VI.] 



The 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 Sheer- 

 ness-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 aud 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 Cre- 

 taceous period. This leads me to refer to the ' Supplement ' No. iii. 

 to the Monograph on the Cretaceous Pterosauria (PalaBontographical 

 Society's volume, 4to, for 1860), in which descriptions and figures 

 are given of the proximal portion of the right humerus of Pterodac- 

 tylus SedgwicMi, Ow., a species about the size of a large vulture 

 (Vultur motiachus, L.), of which bird comparative views of the 

 answerable bone and part are added in the same plate (pi. 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 corre- 

 sponding 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, 



* apyiWos, clay ; opvis, bird. 



