DEVELOPMENT OF THE SKULL IN THE SALMON. 
Ill 
between its broad part and the periosteal wing, to receive a peg from the next pier, and 
by this elegant carpentry the two piers are strongly coupled to each other. 
The free part of the mandibular arch is one third longer than the pier ; it is strongly 
clamped by a bone which is grafted upon it, most on the outer side; this is the 
articulare. 
The “ coronoid process ” is part of this bone, and not due to the Meckelian rod ; but 
the hooked process behind the angular process is due to the character of the original 
segmentation of the terminal piece. The “ articulare ” is snagged, ribbed, and splintered, 
and only ossifies the proximal part of the mandible, the rest being a strong, rounded, 
gradually tapering rod (Plate VIII. fig. 9, ar., ink.). 
As in the Bird there is no “ mento-meckelian ” bone, such as occurs in Frogs and Man. 
No morphologist has ever been more richly repaid for his labours than he who traced 
the metamorphosis of the second “ postoral ” in the Frog ; equal pleasure and profit has 
attended the unveiling of the mystery of the Teleostean hyoid arch. This arch has its 
fullest development, if not its highest metamorphosis, in the Osseous Fish. On each 
side of this huge siving there are seven bones and four broken-up segments of cartilage, 
besides an azygous pier, which has its own bony plate, besides, in the Salmon, thirty-three 
parosteal bones. How all this has been made out of a single pair of facial rods let 
embryology declare. Not now, however; at present let it be assumed that the second 
“ postoral ” does cleave a long cleft down its substance, that the foremost larger part 
stays atop, and that the narrower part slides slowly but surely down to the knee on the 
synchondrosis of the foremost piece. The great factor in the swinging-power of the 
Fish’s mouth is the uppermost part of the larger anterior division of the arch. At first 
hooked beneath the fore part of the auditory capsule, it keeps under a ledge formed by 
the bulging of the horizontal canal, and then the hinder piece having escaped downwards 
out of its way, it grows along nearly to the extreme end of the sac. 
The long scooped facet for this element, the “ hyo-mandibular,” is shown in lower 
and side views of the skull (Plate VII. figs. 2 & 3, and Plate VIII. fig. 2). Below 
the unossified, long, convex condyle of the hyo-mandibular there is a knob for the cup 
on the opercular (ojp.c.) ; below this the bone gradually narrows and stops short above 
the knee like bend ; then comes a broad cartilaginous tract, and below that the ossified 
“ symplectic” peg (sy.), which turns forwards to fit into the groove of the quadrate. On 
the inner and posterior face of the out-bowed synchondrosis there is a small rod of 
largely ossified cartilage, this is the “ stylo-hyal ;” it is the secondary suspensorium of the 
second narrower division of the second “ postoral,” and is attached by ligament to a cup 
above and to a cup below ; there is evidently a small joint-cavity above within the 
ligament, but not below (Plate VIII. fig. 9, st.h.). I do not find this “ stylo-hyal ” (Cuv.) 
until I come to the fourth stage, and it has no separate representative in the Frog ; yet 
in Fishes it is found from the lower “ Ganoids” (the Sturgeons for instance) up through 
all the higher osseous kinds ; not, however, in “ Myxinoids,” nor “ Plagiostomes,” which 
are represented by very early conditions of the Teleosteans. 
MDCCCLXXIII. Q 
