DEVELOPMENT OF THE SKULL IN THE BATKACHIA. 
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studies of the metamorphosing Tadpole (see “ Frog’s Skull,” plate vii. figs. 1-5, and 
plate viii. figs. 1-4, i.hin. — “ infra-hyomandibular,” the erroneous name I gave to it). 
Even the fact that this tract was ossified by a bony plate (in the Common Frog and 
Bull-frog), which I correctly designated as the “ metapterygoid,” did not undeceive me. 
In the third stage (fig. 3) the elbow of the mandibular pier is quite free from any 
otic attachment ; hut in larval forms of several kinds of Batrachia I have found two 
distinct binders, attaching these two unrelated parts together. In Tadpoles of the Frog 
an inch or more in length, and with hind legs apparent, there is a band which runs 
from the elbow, and then becomes pedate, attaching itself to the edge of the tegmen in 
front (“ Frog’s Skull,” plates v. vi. vii., s.hn.). This part becomes detached as a small 
trefoil of cartilage ; it lies outside the “ portio dura,” and becomes the “ annulus tym- 
panus.” The next attachment is by a much larger band, the “ otic process ” of the 
mandibular pier (“ Frog’s Skull,” plate viii. figs. 3, 4, m.jpg.) ; in a further stage (fig. 8) 
it lies above m.jpg. and i.hm. 
In the Toad in this and the next stage it is seen outside the pedicle (fig. 8, ot.jp.) ; it 
has coalesced with the anterior edge of the tegmen, and is invested with the squamosal : 
in the figure, being on the outside, much of the breadth is hidden. 
The rest of the pier is now at right angles with the axis of the skull, and forms a 
large angle with the metapterygoid step on the pedicle : this is the quadrate region : its 
lower surface is obliquely scooped for the sinuous articular part of the free bar (fig. 6, mJc.). 
The pterygoid bar (jpg.) passes off at right angles with the quadrate, by a broad base in 
front of the meeting of the quadrate and metapterygoid regions ; a bony ectosteal plate 
is forming on it, which runs forwards, and will spread upwards and downwards. Here 
we miss that other ectosteal plate which the Frog possesses, namely, the metapterygoid 
(“ Frog’s Skull,” plate viii. figs. 4 & 8 ; it is lettered m.jpg., although attached to i.hm.). 
The hyoid bar ( c.liy .) was seen in the larva (figs. 2, 4) neatly articulated to the man- 
dibular pier below the outer edge, and a little behind ( = above) the outer or pterygoid 
end of the pterygo-palatine bar. Now that the quadrate condyle is opposite the optic 
foramen, instead of being opposite the nasal passage, the hyoid has had to go backwards 
with it. By such a change of position it has come very near to the fore margin of the 
auditory capsule, within easy reach of its external and lower edge, its ultimate destination 
(see Plate 54. figs. 4 & 7). This plate has become a narrow bar ; it has become sundered 
from its neat joint, and its little rounded inturned condyle is now rather loosely attached 
by ligament ; yet it retains, very nearly, its old attachment as to the region of the man- 
dibular pier, which was, from the first, a little behind, or above , the root of the pterygoid. 
The large, oval, externally convex stapes ( st .) is nearer the posterior margin of the 
capsule than the anterior ; its front end is a considerable way behind the condyle of the 
“pedicle;” it is attached to the outer face of the periotic capsule, under a large cres- 
centic eave of cartilage — the tegmen. Only the hinder part of this plug has its inner 
face in contact with the membranous labyrinth, and that part is covered, outside, with 
muscular fibres (m.). All the fore part of the primary dint (fig. 4, au.) is floored with 
