2Q PROP. OWEN ON THE SKULL OE AEGILLOENIS LONGIPENNIS. 



6 lines ; the same admeasurement in Odontopteryx gives but 2 inches 

 6 lines. I estimated the total length of the latter's skull at 5 inches 

 6 lines. Completing on the same scale the broken beak of Argil- 

 lornis (PI. II. fig. 1), the skull gives a length of 7 inches 6 lines. 

 The degree in which the wing-bones of Argillornis resembled those 

 of Diomedea is so nearly that in which any resemblance can be 

 pointed out in the cranial fossil to the skull of the Albatross amongst 

 existing birds, that the probability of the cranial and humeral fossils 

 belonging to the same bird or species of bird from the Sheppey 

 locality of the London Clay appears to me to justify the reference 

 of the present fossil to Argillornis longipennis. If such a skull 

 should be hereafter discovered associated with the rest of the skele- 

 ton, in this or any other locality, so as to disprove such supposed 

 generic or specific agreement, the name Macropteron may, perhaps, 

 be accepted by the fortunate describer of such fossil remains of a 

 new genus. 



EXPLANATION OF PLATE II. 



Fig. 1. Side view of skuU of Argillornis longipennis, 



2. Upper view of the same. 



3. Under view of the same. 



4. Anterior fractured surface of upper bill. 

 6. Posterior surface of cranium. 



6. Exposed part of inner wall of cranium, lodging th.e optic lobe, ojj. 



7. Outline of part of the right side of the upper jaw. 



7 a. Magnified view of the alveolar surface of the small entire part, /, of 

 that side. 



All the figures, save 7 a, are of the natural size. 



Discussion. 



Prof. Seeley remarked upon the disadvantage under which the 

 Fellows of the Society laboured in attempting to discuss the subject 

 when the specimen was not before them. The diagrams, as he 

 pointed out, differed from the description in many important parts. 

 If Prof. Owen's description was rather to be relied upon, he argued 

 that the analogy with the Albatross was not made out. He should 

 have liked to know the evidence on which the skull was associated 

 with the limb-bone. 



Mr. HuLKE stated that the diagrams exhibited were very accurate 

 and intelligent copies of Prof. Owen's sketches. 



Mr. W. Da VIES and Dr. Woodwaed stated that the fossil, which 

 they had both seen, greatly resembled, in general character, the skull 

 of the Albatross. 



