1873.] OWEN DENTIGEROT7S BIED. 517 



reptilian one is grafted, shows profitable comparisons to be within 

 the limits of the feathered class. The inference which has been 

 drawn as to the length of the beak leads us first to compare Odon- 

 topteryx with those birds in which that part also exceeds in length 

 the rest of the skull, which latter portion, bounded in front by the 

 fronto-nasal suture, I shall speak of in the ensuing comparisons as 

 the " cranium." 



Such character is exceptional in the Aves aerece and Aves terrestres 

 of Nitzsch. The Hornbills, Toucans, a few Crows, certain Wood- 

 peckers, Kingfishers, Cuckoos, Humming-birds, Kivis, Ostriches, 

 manifest it, but with well-marked differential characters pointing to 

 another road, for the closer affinity of which we are in quest. 



A beak longer than the cranium is the rule in the Aves aquaticce ; 

 but not any of the waders has the external nostrils so remote 

 from the orbits as in Odontopteryx. This character of the fossil 

 confines one to the Totipalmates and tubinarial Longipennates ; but 

 the Petrels, like the Albatrosses, Gulls, Terns, and Skimmers have 

 other well-marked characters which remove them from the present 

 extinct genus. 



Indeed, the absence of the superorbital gland-pit in Odontopteryx 

 limits the field of comparison to the Totipalmates and Lamellirostrals, 

 in which, however, the Swan (Cygnus olor) and some Geese (Cere- 

 opsis) and Teal show traces, more or less definite, of the impression 

 of such gland above and behind the rim of the orbit. There is no 

 such trace in the Cormorants, Anhingas, and Gannets ; and it is in 

 these fish-eating sea-birds that an extent of upper beak-bone, free 

 from narial vacuities, would be found corresponding with that which 

 is preserved in the Sheppey fossil. But the Totipalmates have not 

 the orbit bounded by a hind wall as in Odontopteryx ; the super- 

 orbital border is abruptly truncate behind by a wide and deep crota- 

 phyte fossa, which in the Cormorant and Gannet ascends so as 

 almost to meet its fellow upon the parietal region of the cranium. 



In Odontopteryx, the parietal region is broadly and smoothly arched 

 (PL XVI. fig. 4, 7) ; and the crotaphyte fossa (PL XVI. figs. 1, 2, s ), 

 very shallow, commences low down at the side of the arch (fig. 1, «), 

 very little above the level of the foramen magnum. Now this is the 

 character of the fossa in certain Anatidce, the Goose (Anser palustris) 

 e. g. ; and in this family, also, the orbital wall is continued down 

 the back part of the cavity as in Odontopteryx, but is there produced 

 forward as a strong process, which seems not to have existed in the 

 fossil. The hinder half, however, of the external nostril would have 

 appeared in the base of the beak preserved in the fossil, if the bird 

 it represents had partaken of the narial characters of the Lamelli- 

 rostrals. 



In most of these water-birds the coronoid border of the mandible 

 is raised into a definable process ; and where, as in Mergus, this is 

 not the case, the outstanding tubercle is present, of which there is 

 no trace in Odontopteryx, as there is none in the Totipalmates. 



The hind half of the mandibular ramus resembles in its depth 

 and thinness that part of the lower jaw of the Lamellirostrals more 



