474 
MR. W. K. PARKER OK THE DEVELOPMENT 
Here the cavity of the skull is at its widest part; further back the width of the head 
is due to the addition of the auditory capsules, but the hind brain (C 3 .) is only half as 
wide as the mid brain (Cl). Here the razor passed from the front of the fontanelle, 
above, to the middle of the fontanelle, below, just where the trabeculae pass into 
the investing mass (iv.), and behind the optic foramina (see Plate 35, figs. 11, 12) ; 
the section is therefore somewhat oblique, backwarxls and downwards. The slight 
projection from the front tegmen ( t.cr .) is wide apart from the alisphenoidal region, or 
lateral band of cartilage ( al.s .), which is thickish, convexo-concave, and occupies more 
than half of the side wall. 
Below, under the thalamencephalon, the parasphenoid (pa.s.) is thick and narrow, 
and is strongly wedged in between the narrowest part of the basal bars (see also 
Plate 34, fig. 3, tr ., iv., pa.s), which are oval in section, and slightly tilted outside. 
Between them and the alisphenoidal tract (al.s.), part of the trigeminal nerve (V.) is 
seen. Above, the parietals (p.) are cut through, and also a lateral bone—the squamosal 
(sq.). Here the suspensorium ( q.) is, in section, like a drumstick, but feeble below and 
out-turned, for it thins down towards its lower thickening, and there bends outwards 
over the small, round symplectic ( sy .). Above, it is round, very solid, and sheathed at 
the very top with a bony tract; this is the “ metapterygoid ” (mt.pg .) which is cut 
through. 
Below, the preopercular ( p.op .) is seen as a small tract of diploe, enclosing a mucous 
gland; inside it, the cerato-hyal, with its ectostosis (c.liy.), is severed, and further 
inwards the basi-branchial and the first and second hypo-branchials ( b.br ., h.br l, b.br 2 .). 
Section 17.—We have now a section (Plate 36, fig. 2) close in front of the pituitary 
body, but missing it; it is through the infundibulum (inf.) below, and the mid brain 
(Cl) above, and catches the terminal point of the small tegminal projection; this thin 
slice was the next to the last, which is not always the case in those which are figured. 
Here the basipterygoid processes (for q. read b.pg.) are seen as thick wings growing 
from the front part of the investing mass ;* they are partly ossified by the lower edge of 
the alisphenoidal centre; they are thin at their root, thick outside, and they dip a little ; 
above them, the 5th nerve (Y.) is cut through. Here the parasphenoid ( pa.s.) sends out 
its first pair of angular projections (Plate 34, fig. 2), so that it forms a bony floor to the 
skull. Above, the parietals and squamosals ( p ., sq.) are seen in section, and also one of 
the numerous post-orbital scales. The symplectic (sy.) is cut off where it has a bony 
sheath, as it passes forwards to the suspensorium. The cerato-hyal (c.hy.) is trilobate 
here in section ; outside, it is the interopercular (i.op.) ; the branchial sections are of 
the same bars as in the last. 
Section 18.—This (Plate 36, fig. 3) is through the fore part of the hind tegmen (t.cr.), 
and where the mid brain passes into the hind brain (C 3 .). Here the head is slightly 
concave above ; the roof-cartilage is rather thin, and forms part of a nearly complete 
cincture, for it is confluent here with the fore part of the auditory capsule (au.) t which in 
* Two errors escaped me in the lettering of this figure,—for q. read h.pg., and for mt.pg. read iv. 
