DEVELOPMENT OE THE SKULL OE THE COMMON EOWL. 
803 
upper head ; below it is deeply notched, where it projects backwards from the mandi- 
bular facets, for the quadrato-jugal, which is curved to wind round the base of the qua- 
drate (see Plate LXXXVII. figs. 4 & 5, q.j., q.). 
The mandibles vary considerably in individuals : in the one figured (fig. 4) there is 
scarcely a trace of the great fenestra seen in the Tetraonidae (Zool. Trans, vol. v. pi. 36, 
fig. 9) ; but in others it is present. There is generally some trace of the suture between 
the posterior wedge of the dentary and the angular and surangular ; but all the other 
sutures close ; the dentaries anchylose with each other early, like the premaxillaries. 
In the hyoid arch the stapes undergoes no further change ; the lesser cornua of the hyoid 
(Plate LXXXVII. fig. 11, c.h.) coalesce to form a glosso-hyal ; but the tip of the coalesced 
cartilage continues soft, and a fontanelle is persistent between the bony part ; this elegant 
sagittiform tongue-piece articulates with the basihyal (b.h.) by a synovial hinge. 
The basihyal is carinate above, and behind articulates by a small synovial joint with 
the long, slender, proximally ossified basibranchial (jb.br.). The branchial arch articulates 
below by a gliding synovial joint to the end of the basihyal; but the proximal piece, 
or “ cerato-branchial ” ( c.br .), is articulated to the distal, or “ epibranchial” ( e.br .), by a 
mass of connective fibre ; the proximal (lower) piece is soft above, and the upper piece 
at both ends. 
When the outer table of the dense aged skull is removed, the semicircular canals 
(Plate LXXXVII. fig. 9, a.s.c., h.s.c., p.s.c.) are seen to be imbedded in a moderately 
delicate diploe : in the figure the outer tympanic walls are removed, and show the fenestra 
ovalis and fenestra rotunda ( f.o.,f.r .) on the surface ; a bristle is shown as passing along 
the tortuous canal for the internal carotid artery. 
The figures, as compared with what is seen in Aerial Birds, show what every one is 
familiar with in the natural skull, namely the non-typical coarseness and strength of 
the whole skull and face *. 
Concluding Remarks. 
Having thus, with as much expedition and brevity as I have been competent to, run 
through the ten arbitrary but not unnatural stages in the morphological history of the 
Fowl’s head, I would conclude by hinting at the importance of the various isomorphisms 
displayed by the skull and face of this one type in its stages of growth. 
1 have described it upwards^ but my long and really anxious labour has been in the 
opposite direction ; the stages were traced from that of the old bird downwards to that 
of the chick of the 4th day of incubation. 
Whilst at work I seemed to myself to have been endeavouring to decipher a palim- 
psest , and one not erased and written upon again just once, but five or six times over. 
Having erased, as it were, the characters of the culminating type — those of the gaudy 
Indian bird — I seemed to be amongst the sombre Grouse ; and then, towards incubation, 
* In a Jungle-fowl ( Gallus bankiva ) which I dissected for Professor Huxxey, the skull was much more 
fibrous and less dense than in the tame Eowl : it was more like that of the Pheasant. 
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