106 
ME. W. K. PAEKEE ON THE STEUCTUEE AND 
the same regions in the Bird ; this distinction is shown in Plate VII. fig. 4, where in front 
of the orbito-sphenoid bone ( o.s .) there is seen a sinuous fissure ( e.t.f, '.). This fissure had 
been seen and drawn by me nearly three years before its development was made out. We 
should soon understand all things that belong to the skull if the sphenoidal regions 
were intelligible ; they are not, however, as yet ; for have we not just seen that even the 
posterior sphenoid is in front of the axial part of the skull, and that it grows out from 
the auditory capsule 1 Not altogether, however, for the alisphenoid is continuous above 
with cartilage which grows backwards from the “ ethmoid,” the ethmoid itself being 
built upon the foundation laid by the “ trabeculae ” — a state of things enough to suggest 
to us the wearing away of morphological landmarks during the ages that are past. At 
present I have to describe the anterior sphenoid as it exists in the adult. Neither in 
the Bird nor in the Teleostean Fish can any part of the anterior sphenoid be seen 
either from above or from below (compare Plate VII. figs. 3, 4, & 10, and Plate VIII. 
figs. 1 & 2, with “Fowl’s Skull,” Plate lxxxvii. fig. 1, os. i, os. 2 ,jps.); in the] Bird the 
mesoethmoid meets the prepituitary part of the basisphenoid, and in the Salmon that 
prepituitary part is scarcely ossified at all by the Y-shaped bone, and the coalesced 
trabeculae and the keel ascending therefrom are permanently unossified. Above also 
(Plate VII. figs. 1, 3, 10, o.s.), the cartilage of the great “ culmen cranii” is not infected 
by the bony orbito-sphenoidal lamina*. 
A vertically transverse section of the coalesced orbito-sphenoicls (there is no distinct 
presphenoid) shows well their structure, and how that they in this case, and not the 
ethmoid, close-in the cranial cavity. There is no “ crista galli,” and the perforation 
(Plate VII. figs. 3, 4, & 10, 1 ) for the “olfactory crus” is in the orbito-sphenoid. In 
the vertical section Ave see the twin bone grafted upon the “ culmen cranii” above, and 
upon the thick swelling partition that grows upward from the shelving trabecuke below. 
This double bone has metamorphosed some cartilage, but, like the \ r -shaped basisphe- 
noid, it is principally membranous ; in the Sturgeon the orbito-sphenoids do not graft 
themselves upon the cartilage, and in the Fowl the two pairs of these bones have no 
orbito-sphenoidal cartilage to graft themselves upon (see “ Fowl’s Skull,” Plate lxxxvi. 
fig. 11, os. 1 , os. 2 ). 
Foundation, side-walls, and roof, — all these are facial in the ethmoidal or nasal region : 
Ave are in front of the skull iioav, and the brain which did overtop and overhang every 
thing else in the head, and was, indeed, the largest thing there, is now relatively a retired 
series of small lobes and bands (compare Plate VII. fig. 4, shoAving the cranial cavity, 
Avith Plate I. fig. 8, showing a sectional view of the head in my earliest stage), so that 
the ethmoidal region can iioav be studied in an extracranial manner ; Ave need not try 
to torture it into the vanguard of the A T ertebrae, or even into a “ cranial sclerotome.” 
Save in expansion and size, the “trabeculae” have undergone but little alteration in 
their under surface since the time of hatching, and even tAvo or three days before ; 
but above they have been subject to great change, by means of the various outgroAvths 
that have sprung from them (Plate VIII. figs. 1 & 2, tr.). Looking at the bare skull 
