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, Chameleo, 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 Reptilia; 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, eth.) 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 (Pl. 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 ; 
