DEVELOPMENT OF THE SKULL IN THE BATKACHIA. 
655 
The nasal capsules are thus seen to be but little indebted to trabecular outgrowths 
for their protection; these latter are somewhat supplemented by the upper labials ( u.l .) 
to be described soon. 
The changes that have taken place in the mandibular arch are easily traceable ; the 
pedicle (figs. 5, 6, p d.) is long, the broad central part of the pier is now lost in the outer 
lobes, which now lie outside the foremost part of the auditory capsule. The two inner arms 
of this plate (compare figs. 3 & 6) are much altered by elongation and attenuation ; and 
whereas the hinder(_pdL)ran backwards to join the trabeculae, it now runs forwards; also the 
front bar, which ran forwards, nOwruns backwards as well as inwards (figs. 5 & 6, epa.). 
The former of these is now a narrow band which is dilated into a broad plate, where 
it joins the trabecula (pd., tr.) ; the latter has grown now into three distinct regions, 
namely, the ethmo-palatine ( e.pa .), the prepalatine ( prpa .), and the common postpala- 
tine and pterygoid bar (pt.pa., pg.). This bar is now sigmoid in shape, and of great 
length ; it sets on to the fore face of the quadrate close within the condyle, and is 
elbowed out just before it joins that part: two longer elbows, but less bent outwards, 
are seen, the first where the palatine runs into the pterygoid region, and the next at 
the root of the leafy prepalatine. This latter part (once the “prenarial lamina ” p.n.l.) is a 
further development of the secondary antero-internal lobe ; the secondary growth on the 
antero-external lobe, the process for the condyle for the hyoid ( hy.c .), is now obliterated ; 
this is a correlate of the absorption of the cerato-hyal (fig. 7). 
The two external lobes are now seen to have become the outturned, scooped quadrate 
trochlea (q.); and the inturned otic process ( ot.p .) a triangular wedge with a rounded apex, 
over which the columella ( it.st ., m.st.) passes. Here the articular portion of the quadrate 
cartilage is a deep trochlear groove, the cartilage being most curved away below ; it was a 
rounded condyle (fig. 3, q.). On the other hand, the articular surface of the free mandible 
(fig. 7, ar.) is a sinuously rounded head, and it was (fig. 3, ar.) a scooped hollow on the 
upper face of the end of the cartilage. The dilated end of the cartilage is covered with 
a bony sheath (fig. 7, ar.) which attenuates gradually forwards, clinging to the inner 
face of the rod, and ending near the symphysis in a point ; this is the ectosteal “ arti- 
culare,” which ossifies the proximal part of the mandible. On the outer side is a bone 
( d .), the dentary; its broad part is in front of the symphysis, where it is tied to its 
fellow, and it ends where the upper third of the bar begins. Much of Meckel’s rod is 
unossified within these two bones ; there is no “ os Meckelii ” or mento-Meckelian 
element. 
The cerato-hyal has disappeared ; I have indicated its empty place by a dotted line 
(fig. 7). In the upper and anterior region of the second postoral arch there is a considerable 
osseo-cartilaginous bar (Plate 60. figs. 5, 6, and Plate 61. figs. 2, 3, 6) ; this is the colu- 
mella : it is attached behind to the stapes (st.), now fully developed. All these things 
are new since the early stage in which all that was formed was a fossa containing gelati- 
nous stroma. I strongly suspect that the development of these embryos is very rapid, 
for the lesser of the young in this stage are but little larger than the recently changed 
