Royal Microscopical Society. 
225 
The large coalesced prae-maxillaries ( px.) are seen overlapping 
the maxillaries (Plate XXXVIII., Fig. 1, mx.), and the retral process 
of these latter bones has now acquired its elegant ear-shape. Seen 
from above (Plate XXXVIII., Fig. 2), the cranial roof is well filled 
in ; a little of the ethmoid ( eth .) is seen, and two remnants of the 
great fontanelle (fo.); and the top of the “ ecto-ethmoid ” (e. eth.) 
projects on each side; afterwards it gets its own osseous centre, 
distinct from that of the “ meso-ethmoid ” (Figs. 2 and 4, pe.), 
and from that of the “pars plana” (p>. p.). This latter part is 
still unossified (see also Fig. 2). The lachrymal ( l .) now occupies 
nearly all its anterior edge. The “ meso-ethmoidal ” hone (p. e .) 
nearly reaches the notch (Fig. 4, c.f. c.) in front, and the interorbital 
fenestra (i. o. s .) behind. The septum-nasi is still soft, as also all 
the anterior sphenoidal region, which has its orbito-sphenoidal lips 
very small. In more advanced young I find a distinct prae- 
sphenoid perched above and between the huge middle ethmoid and 
basi-sphenoid, but no orbito-sphenoids ; the orbital plates of the 
frontals do duty for them in these high, perching types. The 
auditory capsule (Fig. 4) has coalesced with the ex-occipital (e. o.) 
and its own opisthotic (op.) andprootic (pro.) pieces are no longer 
distinct ; the ali-sphenoid (al. s.) is now well ossified ; the knob of 
cartilage projecting from it in the post-frontal region is part of the 
ear-sac — the “ sphenotic.” 
The double nasal sac seen from above (Plate XXXIX., Fig. 3) 
shows the ali-nasal, ali-septal, and ali-ethmoidal regions (al. n., al. s., 
al. e.); in the latter is seen the broad top of the “ meso-ethmoid ”(p.e.). 
This part ends as a blunt spur, above the “ orbito-presphenoid ” (o. s.). 
The transverse sections are through the middle ethmoid, and behind 
the lateral ethmoids in Fig. 5 ; and through the unossified part of 
the middle ethmoid in Fig. 4. This latter section is through the 
upper and lower turbinals (u. tb., 1. tb.) ; the “middle turbinal” is a 
mere rudiment on the front of the “ pars plana,” or antorbital. 
This same section is through the nasals ( n .), nasal processes of the 
prae-maxillaries (p. x.), the maxillaries and their maxillo-palatine 
processes (mx.), the forks of the vomer (v.), and the palatines 
(pa.). A longitudinal section outside the septum (Fig. 6) shows 
the ali-nasal turbinal (a. n. t.), the inferior turbinal (l. tb.), and the 
upper turbinal (u. tb.). 
The mandible (Figs. 2 and 4) shows the “articulare” much more 
ossified, the investing elements much more developed ; Meckel’s 
cartilage {rah.) nearly hidden ; and the coronoid (Fig. 4, cr.) anky- 
losed to the “ articulare.” 
The “ os hyoides ” (Plate XXXIX., Fig. 7) shows an osseous 
tract in each “ cerato-liyal ” (c. h.), and both the pieces of the 
third post-oral (br. 1) have thin osseous shafts. The azygous 
piece (bh., ah.) is still soft. 
s 2 
