606 
MR. W. K. PARKER ON THE STRUCTURE AND 
sphenoidal bar, below by the basisphenoid, and above and behind by a sinuous creeping 
branch of cartilage that forks off from the main, front bar (above its ossified part, 
where it turns outwards, to ascend to the upper band), grows backwards until it 
touches the anterior ampulla ( a.s.c.) and then runs down in front of the trigeminal 
nerve. 
This creeping, posterior bar unites with the basisphenoid, after perfecting the 
foramen ovale (V) ; the main, front bar, of the alisphenoid unites with the trabecula 
by a forked process, close behind the common optic “fenestra" (II). The widest part 
of the cartilage is at the top, behind; to it is tied the cartilaginous top of the bony 
post (epipterygoid, e.pg.). 
The lower, well ossified part of the main bar, behind the optic nerves, is always seen 
in dry skulls of the Lizards, but the cartilaginous parts are seldom seen.* 
The rest of the cranio-facial axis of Lacerta is as instructive as the posterior 
sphenoidal region : it is curiously like, and curiously unlike, that of the Bird. 
The orbito-sphenoid (o.s.) is much larger than in the embryo of Struthio, and is 
deeply notched in front. At its root it is narrow, and only at that part is it joined to 
the presphenoid ; its hind lobe is continuous with the alisphenoid, at the top ; and the 
sharp, lesser, long, front, lobe ends in a free point a little way behind the nasal wall 
(Plate 43, figs. 2, 7, 8, o.s., p.e.). 
The presphenoid runs from the optic foramen (II) to the ethmoidal region (p.e.), 
which is partly marked off by a rudiment of the fenestra—the familiar cranio-facial 
cleft, of the Bird (figs. 1, 2, c.f.f.). 
This “ fenestra,” which does not exist in the “ Ratitse,” but appears in some of the 
semi-struthious Tinamous (“Ostrich’s Skull, Plate 15, fig. 8), and in the Chick by the 
end of the second week of incubation (“Fowl’s Skull,” Plate 83, fig. 4), is also present 
in the Australian Stump-tailed Lizard (Trachydosaurus rugosus), but not in the 
Chamseleon. 
Here, it has only a morphological meaning; in the Bird it helps to finish a series of 
the most marvellous metamorpliic specializations ever seen in the Vertebrate skull; in 
the Crow, the Parrot, and the Toucan, its final meaning comes out with its finish in 
the cranio-facial hinge. 
The very constant interorbital fenestra of the highest “Sauropsida” is here in 
Lacerta. It is a large, superior interorbital notch ( i.o.n .), larger than the notch behind, 
where the optic nerves pass out. The slanting stem of the presphenoid becomes 
partially ossified in age (Plate 43, fig. 8, p.s.) ; and there is some bony (endosteal) 
deposit under those nerves. 
* After more than twelve years, the small distinct ali-and orbito-sphenoids of the Snake ( - ‘ Snake’s Skull,” 
Plate 29, fig. 5, al.s., us.) cease to be inexplicable to me ; they are, in that arrested chrondocranium, mere 
patches of what is seen in Lacerta. The Snake’s alisphenoid is just so much as lies in front of the exit of 
the 5th nerve in Lacerta, and its orbito-sphenoid, a rudiment of that of the Lizard, behind the forks. 
