1873.] OWEN DENTIGEKOUS BIED. 521 



"When we are favoured, with the description and figures of the 

 Odontorniihes by their accomplished discoverer we shall possess 

 grounds for judging of the ordinal and higher relations of affinity 

 between the Eocene toothed bird and the Cretaceous Ichthyornis. 

 But the indications already vouchsafed by that active and inde- 

 fatigable palaeontologist suffice for an opinion of their specific and 

 generic distinctness. 



Odontopteryx* has the orbits well within the limits of the hinder 

 half of the skull ; the lower jaw, though no doubt " long," has the 

 rami too deep to bear the term " slender ; " the teeth are separated 

 by spaces which would not permit of their being reckoned as " quite 

 numerous ;" they are not implanted in sockets, but are represented 

 by alveolar processes of the bone. It is true that some of them are 

 "small," and all are "compressed and pointed;" but they are not 

 " all similar " in respect of size : one, two, or three small teeth are 

 interposed to the single, widely separated, large laniaries ; finally, 

 all the preserved teeth of Odontopteryx incline more or less forward 

 instead of " backward." 



EXPLANATION OF PLATES XVI. & XVII. 



Plate XVI. 

 Fig. 1. Eight-side view of the preserved part of the skull of Odontopteryx toli- 

 apicus, Ow. 



2. Left-side view of do. do. 



3. Hind or occipital surface, with right tympanic bone : v, portion of atlas. 



4. Upper view of the preserved part of the skull of Odontopteryx toli- 



apicus, Ow. 



The above figures are of the natural size. 



5. Preserved dentigerous parts of right side of both jaws ; twice the natural 



size. 



6. Preserved dentigerous parts of left side of both jaws ; twice the natural 



size. 



7. Outline of entire skull, conjecturally restored, from above. 



8. Outline of entire skull, conjecturally restored, from the right side. 



Plate XVII. 

 Fig. 1. View of a longitudinal section of the denticle, magnified 35 diameters 

 and reduced one half. 

 2. View of a portion of the same section, magnified 250 diameters and 

 reduced one half. 



Discussion. 



Mr. Seelet had given much study to the Pterosaurians, to which 

 the author had indicated the affinities of Odontopteryx. He had in 

 Orniihocheirus Oweni found what appeared to be identical structure 

 with that of the bird ; and it therefore appeared to form a new genus 

 of Pterosaurians. Both in the frontal and occipital regions of the 

 skull he recognized affinities to Orniihocheirus ; but it presented 

 even more distinctly marked reptilian affinities. The position of the 

 brain was also quite as far back in the skull ; and the quadrate bone 

 also presented curious analogies, so much so as to be almost identical. 



* I should have preferred the term Odontomis for my genus ; but it is bespoke 

 for Marsh's subclass. 



