612 
ME. W. K. PARKER OK THE STRUCTURE AND 
Here the narrowing palatines are seen to overlap the pointed fore end of the 
pterygoid (pa., ye/.), and the jugal is obliquely severed over the maxillary (j., mx.). 
This section shows no more of the prefrontal, for it is through the crystalline lens, hut 
it shows the size and strength of the frontal and superorbital roof bones (f, s.ob.). 
The 13 th section (fig. 3) is through the post-orbital region, the widest part of 
the hemispheres (C 1<7 ) and the optic “Chiasma” (II), here the notched back of the 
sinuous inter-orbital septum (presphenoid, p.s.) is cut through, and the upper unossified 
stem of the alisphenoid (al.s.) ; the bony stem has just been missed and is indicated 
by dotted lines. 
Over the whole we see the hind part of the frontals, the super- and post-orbitals, 
and the jugals (f, s.ob., pt.o.,j.) ; below, the pterygoid ( pg.) comes into view. 
The 14th section (fig. 4—more than half) is through the mid brain (C 2 ) in front of 
the exit of the 5th nerve and behind the 2nd, and close in front of the pituitary body. 
Simple as this section seems in the figure, it is full of interest, for it displays some of 
the most remarkable things seen in the skull of a Sauropsidan, or indeed of any 
Vertebrate whatever. 
The trabeculae are severed in the pro- clinoid region, before they have coalesced, as 
they do, a little further forwards, to form the base of the orbito-nasal septum. 
There are two other basicranial elements at this part, for the basisphenoid (b.s.) has 
here coalesced with the small rostral parasphenoid (Plate 43, figs. 1, 2, 8, pa.s .); and 
it is worthy of remark that this is the exact place at which the parasphenoidal rostrum 
grafts itself upon the converging trabeculae or becomes ectosteal, in the Chick, at the 
middle of incubation (“Fowl’s Skull,” Plate 82, figs. 1, 2, 3, b.s.). 
Outside the bone (b.s.) a thick plate of cartilage has been cut through, then there is 
a synovial cavity, and then outside that another similar plate of cartilage. 
This is precisely what takes place in the Chick (ibich, Plate 83, figs. 13, 14), which 
differs from the Ostrich (“ Ostrich’s Skull/’ Plate 7, fig. 4; Plate 8, fig. 2, ap.) in 
having a new segment of cartilage superadded to the basis-cranii on each side, the 
distinct equivalent of the “ basi-pterygoid,” which grows directly out from the 
trabecula on each side in the Python, Boa, Ostrich, Guinea Pig, Sheep, &c., and 
which in the Pig rises up the side of the alisphenoid and becomes the “external 
pterygoid plate” (“Pig’s Skull,” Plate 34, fig. 2). 
In those Carinate Birds that develop the basi-pterygoids for articulation with the 
lateral facet of the pterygoids, namely, Fowls, Geese, Pigeons, Plovers, Petrels, Owls, 
&c., these parts are developed as in this Lizard, in which I expected to see a generalized 
condition of these parts, as in the Ostrich. 
The pterygoid (pg.) here, also, acquires a facing of articular cartilage on its upper 
surface, and another joint cavity for a stem of bone ending in cartilage, both above 
and below—the “ epi-pterygoid ” (Plate 42, fig. 3; Plate 43, figs. 1, 2, 7, and 8; 
and Plate 45, fig. 4, e.pg.). 
This bone, which thus rests upon the pterygoid and props up this iveak skull, is here 
