766 
ME. W. K. PAEKEE ON THE STEUCTUEE AND 
head of the quadrate projects some distance behind that of the stapes; but this truly 
ornithic modification is, exceptionally, only of short duration in the Fowl. 
At present the stapes is relatively a much more massive bar than afterwards ; seen 
from the front and side (Plate LXXXI. figs. 9 & 10, 24 diam.) it appears as a flattened 
rod, curved forwards, with an oval head and a trilobate flattened base, the leading ray 
of which is most curved forwards and outwards*. 
There is still a considerable tract of cartilage to be described in the proximal part of 
the face, namely the ptery go-palatine bar. The prenasal cartilage (already described) 
is an azygous prestomal counterpart of the Meckelian rods, although it does not become 
cloven from the primordial skull, and is never related to a free proximal cartilage, like 
the Meckelian bars ; but the pterygo-palatine bar is perhaps the most difficult part of 
the cephalic skeleton to interpret. Seeing its primordial independence of the skull in 
the chick, and noting its early subdivision into a posterior short, and an anterior longer 
bar, it seems to be very feasible to compare its two divisions with the quadrate and 
the Meckelian rod. It lies above and in front of the great stomal cleft, much as the 
mandibular rods lie below and behind ; but its point of suspension is a great difficulty ; 
and the mind of the observer will revert to its various development in the Ichthyopsida. 
In the Chimseroids and in the Lepidosiren this part is not only continuous with the 
skull-base, but also with the prenasal cartilage in front, and with the common pier of 
the mandibular and hyoid arches (Muller, 4 Myxinoids,’ pi. v. fig. 2 ; and Huxley, op. 
cit. p. 196, fig. 78, and p. 209, fig. 85); in the Frog the palatine passes, anteriorly, 
directly into the prefrontal cartilage (op. cit. p. 216, fig. 87). In the chick, the position 
of the pterygo-palatine bar is below and external to the basis cranii (figs. 5 & 6), from 
which it is separate from its first differentiation ; it has, however, a much more intimate 
connexion with the quadrate, but is well differentiated from it on the fourth day 
(Plate LXXXI. fig. 1 ,p.q . , q.), and, indeed, has very different t histological characters. The 
suspensorial parts of the pterygo-palatine bar are feebly developed, and are late in their 
appearance ; these come to be below the optic foramen for the pterygoid, and below the 
prefrontal plate for the palatine : these will be described hereafter. At present the rela- 
tion of the palatine bar to the prefrontal plate (fig. 6, p.p., pa.) is totally unlike what 
is seen in the Frog ; for, between the two, there is not only the thick fibrous stroma in 
which the delicate palatine bar is imbedded, but also the open channel which connects 
the cavity of the mouth with the interior of the nasal labyrinth. I would much rather 
interpret this bar by its specialized and freed condition in the Bird, than by what is seen 
in the low Vertebrate types, where the rampant growth of cartilage masks the proper 
morphological boundaries ; and yet even in the high type the bar would seem to bear 
two interpretations — namely, that it may be a single arch, like the mandibular, 
the pterygoid being the equivalent of the quadrate ; or, on the other hand, the pterygoid 
and the palatine may be merely the proximal parts of two arches, neither of which has 
* This bar must be studied at an earlier stage ; in Cyclodont Lizards and Chamseleons the trilobate (hyoid) 
portion is quite distinct from the clubbed periotic rod. 
