214 MR. W. K. PARKER ON THE OSTEOLOGY 



for those birds differ in tiiis from all others examined by me. The finest instance of 

 this curious connation of the upper part of the lateral ethmoids or prefrontals is in the 

 Cassowaries, where this part forms primarily the whole of the huge helmet. Between 

 the upper or crista-galli bar of the ethmoid and the lower face of the frontals there is 

 a space (PI. XL. fig. 3. 1), large and clavate, common to both orbits, and containing 

 the olfactory crura in the fresh state. A thick bony wall stands between these crura in 

 front, the sides of which they groove : above this groove is the broad " ahethmoidal " 

 part, which I suppose to be separately developed (fig. 3). Mesiad of the lachrymal, 

 this bony disk sends from its outer edge a papery lamina a line and a half broad ; this 

 plate, which is often separately developed as a small upper prefrontal in typical birds, 

 passes inwards and backwards, and then suddenly downwards, where it is continuous 

 with the " pars plana ossis ethmoidei." Where it joins that plate it sends another bony 

 plate forwards, parallel with the middle ethmoid. The " pars plana," or continuous 

 homologue of the separate antorbital of typical birds, is confluent externally with another 

 bony plate which articulates with the inner edge of the descending lachrymal. This 

 outer antorbital plate is the base and back of the largely developed "inferior tur- 

 binal " — so complex in the Ostriches and Mammals, and so simple in typical birds. 

 In the latter, however, it is often more or less ossified, either at its root above or at its 

 termination in front of the orbit. The upper oblique plate protects the olfactory lobe 

 at its termination, and is the bony root of the mostly cartilaginous " superior tur- 

 binal." This must be very small in the Tinamou, for its posterior face is pressed 

 forwards against the skull-axis, leaving it a mere slit-like chamber; moreover in 

 this bird the middle ethmoid is merely scooped gently between the superior turbinals, 

 and not reduced to membrane as in the Emu and certain typical birds, as the Wild 

 Duck (Anas boschas). 



The middle turbinal (fig. 3), which has at its back the "pars plana" or "lamina 

 papyracea," is but feebly developed also in this as in other Struthionidse ; and it is also 

 badly differentiated from the postero-internal folds of the more complex inferior turbinal. 

 In typical birds there is a falling-off of the chondrifying process in the rhinal capsules, 

 and the antorbital portion of the cartilage is laid on in distinct patches ; so that the antor- 

 bital plate of birds, although answering to the " pars plana" of the continuous lateral 

 ethmoid of Mammals and Ostriches, is really autogenous in both its cartilaginous and 

 bony stages : it only answers to the lower part of the massive lateral ethmoid or pre- 

 frontal of the fish. The antorbital of the Tinamou has not joined the middle ethmoid ; 

 it is quite a separate bone ; but the cartilage of the whole lateral ethmoid was, I have 

 no doubt, continuous with the alse at the top of the ethmoid. The posterior part of the 

 great outer fold of the inferior turbinal of the Tinamou is ossified, and an elegant secondary 

 plait within that ; also some threads of bone higher up and further forwards, where the 

 outer wall of this turbinal Hes inside the lachrymal ; and the descending crus of the nasal. 

 Evidently this is all in advance, looking mammal-ward, of what is seen in typical birds ; 



