PEOF. O-VVEN ON THE SKULL OP ARGILLOBNIS LONGIPENNIS. 25 



is 2 inches 6 lines =63 millims. ; the length of the palato-naris, pn, 

 is 1 inch 7 lines =40 millims. ; the extreme breadth of this open- 

 ing is 5 lines =10 millims. It is closed behind by the prgesphe- 

 noidal rostrum, 9, fig. 3, which is wedged between the bones 

 24' & 20'. 



The most prominent character of this part of the bony palate pre- 

 served in the x^resent ornitholite is the degree in which it descends 

 below the level of the alveolar border to form that of the palato- 

 naris. In this character I find the nearest approach to the Albatross 

 {Diomedea exulans). In this bird, along nearly the hinder half of 

 the upper bill, the palatal process of the maxillary forms a ridge, 

 divided by a groove or channel from the alveolar border, which 

 channel gradually widens and deepens, chiefly by the descent of the 

 ridge below the level of the alveolar border, opposite the termina- 

 tion of which the maxillary palatal ridge becomes obtuse, and is 

 flattened and expanded where it is underlapped by the fore end of 

 the palatine. If the alveolar ridge was shaved off short of the 

 bottom of the groove, so much of the groove as is left in the orni- 

 tholite between the outer fractured border and the inner down- 

 sloping maxillo-palatine bones would be represented. Eub the pala- 

 tine part of the maxillary forms no ridge in the fossil ; the flattened 

 surface is continued forward in advance of the underlapping part of 

 the palatine bone. In the Pelican the downwardly produced parts 

 of the palatines are posterior to the palato-naris. The Albatross 

 among existing birds presents the nearest, though a remote, resem- 

 blance to the palatine characters of Argillornis. 



From Biomedea, Argillornis^ like Odontopteryoc*^ differs in the 

 absence of the.basirostral external nostrils and of the superorbital 

 gland-pits. It resembles Odontopteryx in the absence of mesial or 

 lateral ridges, indicative of the temporal fossae, which characters are 

 strongly marked in the Cormorants and other Totipalmates lacking 

 the superorbital gland-pits. The fore part of the long frontal is re- 

 latively broader in Argillornis than in Odontopteryx, and the fronto- 

 nasal suture is consequently more extensive. The upper tract of 

 the upper bill is less defined than in Argillornis ; the basilateral 

 tract leading to the hinder commencement of the longitudinal lateral 

 groove is broader or deeper. This groove, commencing, as in Odon- 

 topteryx, below the praelacrymal vacuity, runs along nearer the al- 

 veolar border than in Odontopteryx. The state of the latter fossil 

 precludes a comparison of the palatal structures ; and the circum- 

 stance that the specimen is unique forbids the making of sections of 

 the more important parts which such comparison would require. 



I have remarked in a former paper t that the skull of OdontO' 

 pteryx seems too small for a bird with a wing-bone of the size of 

 that of Argillornis ; but this objection does not apply to the present 

 cranial fossil. 



The length of this cranium from the upper border of the occipital 

 foramen to the fore border of the praelacrymal vacuity is 3 inches 



* Quart. Journ. Greol. Soc. vol. xxix. 1873, p. 511, pis. xyi. & xvii. 

 t Ibid. vol. xxxiv. 1878, p. 128. 



