DEVELOPMENT OF THE SKULL OF THE COMMON FEOG. 
155 
In the second stage (Plate IV. fig. l)the second poststomal was seen to be lower than 
the first ; and now, attaching itself to the prootic region, it is carried both outwards 
and downwards. 
This upper distinct part is small ; it answers to only the upper part of the Teleostean 
hyo-mandibular ; there is a broad sub-bifid upper head answering to the two ichthyic 
condyles, then a narrow neck, and then behind and below an “ opercular process” (op.p.). 
Below this the two arches are fused together; but the hyoid part is demonstrated just 
above the commencement of the lower third, by the lunate fossa for the “ styloid con- 
dyle ” (Plate V. figs. 2 & 4, st.li.). 
No further light will be thrown upon the amount of “ symplectic ” growth below the 
hinge ( sy .) until we come to the next stage. The free terminal portion of the second post- 
stomal bar has now become a very broad and massive plate of cartilage, the “ stylo-cerato- 
hyal” or “hyoid cornu” (Plate V. figs. 1, 2 & 5, hy.) ; it is roughly 4-sided or lozenge- 
shaped, smoothly convex without, scooped within into an antero-inferior and a postero- 
superior fossa, divided by a ridge which passes down from the semilunar condyle. Only 
the posterior part of the basal line of this plate articulates with the small pisiform 
“ basihyal,” as we saw in the last stage (Plate IV. fig. 12, and Plate V. figs. 2 & 5, 
IX). 
The four remaining arches (branchials) have arrived at their full development, and are 
greatly modified since the last stage (compare Plate IV. figs. 7, 11 & 12, and Plate V. 
figs. 1 & 5, hr.). In the first place they have all coalesced together both above and 
below (Plate V. figs. 1, 1® & 5). Three of the apices can still be seen (fig. 1®, p.br.), but 
there is only one finger-shaped pharyngo-branchial above the first and second arches. In 
meeting above they form a miniature gothic arch, and the secondary bonds are thin and 
fenestrate ; the two regions when they are joined are the “ pharyngo- and epi -branchial.” 
Below, they all unite to form a continuous “ hypobranchial ” region (Plate V. fig. 5, 
h.br.), which articulates on each side with the round first basibranchial and its rudi- 
mentary second segment. This hypobranchial plate, behind the basal element, overlies 
the pericardium (fig. 7, k.br., pc.d.), and lies on nearly the same plane as the summits 
of the arches, close beneath the mucous membrane of the throat ; so that the arches, 
which were once immediately beneath the skin and parallel with the sides of the face 
(Plate III. fig. 3, br.), now hang like hammocks obliquely across the throat (Plate V. 
figs. 5 & 7, and Plate VI. fig. 5). The whole mass on each side looks like a fruit, the 
carpels of which are in a state of dehiscence. 
This resemblance is increased by the form of the first and fourth arches ; in the last stage 
these were acquiring an angular form as seen in section (Plate IV. fig. 12, br. 1 & br. 4); 
but now they are baggy and crumpled, and are extremely thin. The toothings seen on 
their edges, which more or less alternate with each other, are covered with papillae ; 
but these are not calcified into teeth as in the Cod-fish and other “ Teleostei,” but form 
a rich series of transversely placed tufts — branchial tufts (Plate VI. fig. 5) ; in the figure 
the outer tufts are not shown, but they are indicated in Plate V. fig. 7. In a note 
y 2 
