1873.] OWEN — DENTIGEROTTS BIRD. 519 



of Humming-bird has the same character, whence the name " An- 

 drodon." The Dodlet (Didunculus), of the Samoan Isles, has been 

 called the "tooth-billed Pigeon," because of the notches leaving 

 three pointed horny processes in the sheath of the lower bill, beneath 

 and just behind the hook-like production at the end of the upper one. 

 The alveolar borders of the bill in Anatidce and Phcenicopteridm are 

 notched by transversely set lamina? : and these are produced and 

 pointed in their fish-catching allies, the Goosanders and Mergansers. 



But in all these cases the " teeth" of the ornithologist or " tooth- 

 like processes " are horny, are confined to the sheath of the bill, 

 and there are no corresponding productions of the supporting bone, 

 the alveolar borders of which are even, or but minutely indicative of 

 the horny teeth. It is true, as Geoffroy St.-Hilaire first pointed out, 

 the beginnings of the horny sheath are due in some birds (Parrots, e.g.) 

 to detached papilla? occupying shallow cavities of the borders simu- 

 lating sockets ; but the primitive tubercles run into each other, and 

 are ultimately confluent with the beak-sheath*. 



Perhaps a nearer approach to a dental structure is made where 

 the hardening salts are in such excess as to give the sheath the 

 character of ivory, welded to the bone, as in some Woodpeckers. 



The production of the alveolar border into bony tooth-like pro- 

 cesses is peculiar, according to my present observation of birds, to 

 Odontopteryx. The closest repetition of this structure which I have 

 yet seen is in the Australian Hooded Lizard (Ohlamydosaurus) ; but 

 the teeth are small, save the two at the fore part of each upper jaw 

 and the single one at the same part of each mandibular ramus. 

 The smaller teeth are so closely confluent with the alveolar border 

 of both jaws as to seem to be processes : the larger anteriorly ter- 

 minal teeth, though anchylosed to the bone, have their base defined 

 by a ridge, suggesting the outlet of a socket, which is best marked 

 in the lower jaw. All these teeth are tipped or capped with hard 

 dentine ; but such is not the case with the bony tooth-like processes 

 in Odontopteryx. These seem, moreover, to have been sheathed with 

 horn, or to have supported tooth-like processes of the homy beak ; 

 and their outer surface shows, though more feebly marked, the linear 

 and punctate indentations relating to the vascular attachment of 

 the horny to the bony beak. There is no trace of alveoli, although 

 the cavity in the base of what seems to be a broken-off tooth at the 

 fore part of the right upper jaw might be mistaken for one. I have 

 not been able to detect, by application of lenses of any available 

 power to the teeth in situ, any indication of a dentinal cap or apex. 



After having myself outlined the drawings (which were finished 

 as in figs. 1-6, PI. XYL, with the care and accuracy characteristic of 

 the accomplished artist, Mr. Griesbach) I had a mould and cast 

 taken of the unique fossil to represent its original condition, and 

 then selected the dental process which seemed best to promise 

 evidence of tooth-structure. 



Of this tooth (PI. XVI. figs. 1 & 5, e) a longitudinal slice was taken 

 (as in PI. XVII. fig. 1) and laid, with some loss of the apex, upon a 

 * Anat. of Vertebrates, ii. p. 145. 



