OF GALLINACEOUS BIRDS AND TINAMOUS. 213 



normal; only it is rarely developed. In osseous fish generally, the "preorbital" or 

 lachrymal communicates with the true postfrontal by means of a chain of these dermal 

 or at least subcutaneous bones. In Lizards generally, e. g. Monitor, Chamceleo, var. spec, 

 Anolis, Mocoa, Trachydosaurus, Centropyx, and also in the subophidian Anguis fragilis 

 the preorbital or lachrymal has beneath it the first of the suborbital series. This 

 ichthyic bone, which the Lizard has retained, is however coexistent with another sub- 

 cutaneous bone — the "postorbital." I boldly adopt this term for the so-called post- 

 frontal of all the Reptiha ; for I have not as yet found any instance in which this bone 

 is developed in that class from anything but subcutaneous connective tissue : the 

 cartilaginous skull in the Reptilia is in most cases a mere floor, and in the Ophidians 

 the alisphenoids soon coalesce with the sides of the basitemporals. Some of the 

 large Pythons show the bearing of these bones well : there is no prefrontal and no 

 postfrontal; but the eyeball is most safely protected above by the superorbital, 

 behind by the postorbital, in front by the preorbital or lachrymal, and below by the 

 maxillary: all these are splint-bones, and have no existence in the primordial carti- 

 laginous skull. 



We never, at one time, have the roots of the eyelids completely set in bone ; yet the 

 thing is possible, and if the Parrot and Tinamou were added together in one bird, that 

 condition would exist in such a bird. I am not unaware that the superorbital ossicles 

 of the bird do not ossify quite so much of the dermal fibres as in the Lizard : yet they 

 are fairly the true homologues of each other. Even the "squamosal" itself in the 

 Ophidian is rather developed from the connective tissue lying between the membranous 

 skull-wall and the skin, than from the deeper layer on which the frontals and parietals 

 are developed. The occurrence of " scincoid " characters in a bird of so remarkably 

 general a nature as the Tinamou is of scarcely less importance than would be the 

 presence of feathers in some generalized member of the Reptile-class : that is my 

 apology for the above detail. 



As far as I can see, the "middle ethmoid" (PL XL. fig. 3, e«A.) has ossified all the 

 remainder of the cranio-facial axis left untouched by the small anterior sphenoid ; the 

 least fore-and-aft extent of the latter bone is half a line; of the former, the ethmoid, 

 nine lines ; whilst the entire extent of this bony plate, from the exit of the olfactory 

 crura to the end of the nasal septum, is sixteen lines. In the first place, the great 

 size of the vertical ethmoid, as compared with the presphenoid, is quite ornithic ; and in 

 the second place, the growth forwards of bony matter from that plate into the septum 

 shows the arrested general Ostrich-type of structure. In the Rhea I have found a 

 small upper septal bone (PI. XLII. fig. 4, s.n.), three lines long ; but none in the Tinamou 

 — the answering part, and that only, remaining cartilaginous. I suppose that in the 

 Tinamou, as in other Ostriches, the broad top of the ethmoid is separately developed 

 by a long piece growing from above downwards between the anterior ends of the 

 frontals. No suture remains to tell me that ; but if it be so, all is perfectly struthious ; 



