PROP. OWEN ON ARGILLORNIS LONGIPENNIS. 129 



note : — " This change in the name has been made in the paper re- 

 ferred to whilst passing through the press." 



EXPLANATION OF PLATE VI. 



Fig. 1. Argillomis longipennis. Proximal end of left humerus, palmar surface. 



2. The same, aneonal surface. 



3. Proximal end of right humerus, proximal surface. 



4. Diomedea exulans. Proximal end of left humerus, aneonal surface. 



5. The same, palmar surface. 



6. The same, proximal surface. 



7. Argillomis longipennis. Proximal portion of the shaft of left humerus, 



aneonal surface. 



8. The same, radial border. 



9. The same, transverse section distad of pectoral ridge, showing size of 



pneumatic cavity and of its compact wall. 



10. Distal portion of the shaft of left humerus, transverse section above I, 



fig. 11. 



11. The same, palmar surface. 



12. The same, radial border. 



13. Diomedea exulans. Proximal portion of shaft of left humerus, aneonal 



surface. 



14. The same, transverse section distad of pectoral ridge. 



15. Distal end of left humerus, palmar surface. 



16. Argillomis longipennis. "Ulnar side of distal end of fig. 7, showing a 



groove, o, leading to the pneumatic cavity. 



17. Diomedea exulans. Corresponding side of fig. 13, showing the groove 



leading to the " foramen arteriae nutritiae " in Diomedea. This 

 additional evidence of the humeral nature of the portion of bone of 

 Argillomis (fig. 7) was detected and pointed out to me by the ac- 

 complished artist Mr. C. L. Griesbach, F.G.S. 



Discussion. 



Prof. Seeley said that it was impossible to form a judgment upon 

 the matters brought forward by Prof. Owen without an opportunity 

 of closely examining the specimens. At the same time he had no 

 doubt that the remains were those of a bird ; and he had himself, 

 several years ago, obtained in the same locality a bone (a cast of 

 which he exhibited) which he regarded as part of the tibia of a very 

 large bird, and referred to a genus which he called Megalornis. 

 At the time that his paper on this specimen was written, he was 

 not aware that the name had been already appropriated, although 

 he had consulted competent ornithologists on the subject. With 

 regard to the specimens described by Prof. Owen, there might perhaps 

 be some doubt whether all of them belonged to the fore limb, since 

 two of them, he thought, cloFely resembled parts of a tibia such 

 as the tibia of Megalornis. If this resemblance were not an accidental 

 coincidence, the remains exhibited might furnish indications of two 

 genera. 



The Author, in replying, remarked that the bone which Messrs. 

 Bowerbank and Seeley had held to be " tibial," and of an Emuine 



Q. J. G. S. No 133. k 



