DEVELOPMENT OE THE SKULL IN THE SALMON. 
141 
The ossified sheath of the notochord ( nc ., bo.), the median, hollow, styloid rudiment 
of the “ basioccipital,” has not much atfected the posterior half of the “ basilar plate,” 
as yet*. 
One of the peculiar characters of the palato-pterygoid bar is its projection beyond 
the prefrontal attachment ; it is a part well marked in the newly metamorphosed Frog 
(“Frog’s Skull,” Plate vn. fig. 11, pr.jpa.), The Lamprey, evidently related to the pro- 
totype of the Frog, has it also in the same degree (Muller, ‘ Myxinoids,’ pi. 4. fig. 3, 
under mew), although in that low Fish the half-suppressed bar corresponds on the whole 
with my fifth stage, or Tadpoles that have begun to acquire limbs. 
The long suppression and the secondary character of this bar made me waver for a 
long while as to the true morphological character of this arcade ; but I have no doubts 
left now, and shall speak of it unhesitatingly as the “second preeoral arch.” The pre- 
palatine spur is normal enough when it is regarded as the terminal part of a facial 
rod ; and the points of attachment of this bar are easily understood to be consistent with 
the habit of these arches generally, as they are always catching hold of each other to form 
a basketwork. Posteriorly this bar does not connect itself with the trabeculte, as in the 
Lizard and the Bird, but its apex is completely fused with the fore edge of the pier of 
the mandible, with the well-known “ orbitar process.” Tinder the fore part the palatine 
ectostosis (Plate Y. fig. 8, jga.) bearing teeth has begun to invest the cartilage ; below the 
hinder part, and more within than without, is the “ pterygoid ” plate (]>(]■) ; and over the 
middle part is the “ mesopterygoid,” an ovoidal shell of thin bone with its hollow face 
looking inwards (m.pg.) f. 
At the apex of the lowered mandibular pier the ear-shaped “metapterygoid” (mt.pg.) 
has worked into the fore half of the cartilage ; and below the “ quadratum ” (q.), which 
began on the outside , as in the Frog, Newt, and Lepidosiren, has grown to a very elegant 
flabelliform bone with a periosteal posterior wing that is grooved on its inner face, and 
into which the svmplectic is inserted obliquely, like a badly driven nail. The unossified 
quadrate angle forms an elegant condyle, which fits into a deep fossa in the “ articular ” 
end of Meckel’s cartilage ; this, with its largely projected angle, is very much like the 
human “ ulna;” the joint is a simple hinge. In front of the angular and articular region 
Meckel’s cartilage retains its old cylindrical form, and has its rounded end incurved as 
at first. Much of the lower edge is occupied with a lanceolate “ articulare ” full of 
spongy hollows, the primary lamina subdividing again and again (see Fifth Stage, Plate 
III. fig. 9, ar.). 
The “ hyo-manclibular ” ( li.m .), although made now the common suspensorium of these 
* It is easy to see that if the vertebrate animal had been, in each or any case, anencephalous, then the 
materials were at hand, in the notochord, its sheath, and the basilar plate, for several vertebrae, which would 
have elegantly diminished in size from behind forwards ; the tantalizing Amjohioxus merely throws a “ will-o’- 
the-wisp ” light on this dark margin of vertebrate morphology. 
t In determining these bones in other types, it should he recollected that the “ palatine ” plate is under and 
outside, the “mesopterygoid” over, and the pterygoid under and within ; this may help the palaeontologist with 
his “ Ganoids” and other extinct types. 
