DEVELOPMENT OE THE SKULL OE THE COMMON EOWL. 
789 
The premaxillaries, anterior to their mesial coalescence, are normally ichthyic, with 
the exception that each bone developes a palatine process (fig. 6), as in the Mammal. 
But the maxillary (figs. 6-8, m.x .) of the Fowl, above that of all other Birds, is ichthyic 
in a very remarkable manner ; it is a perfect “ os mystaceum and if the papillae of the 
horny beak covering the premaxillaries may be considered (as in truth they are) to be 
potential teeth, then the maxillary is absolutely edentulous as in ordinary Teleostean 
Fishes: it is a very small, delicate style of bone, and, as in the Fish, has a double head, 
the anterior division articulating with the premaxillary, and the posterior with the pala- 
tine ; as in the Fish, the posterior process is turned backwards. 
The manner in which the Bird looks both ways (backwards to the Fish, and forwards 
to the Mammal) is well shown in the maxillary. In those low untypical Rodents, the 
Leporidee, the dentary portion of the maxillary is abortively developed in front; and 
the second division of the palatine part of the Fowl’s maxillary reappears in them as a 
narrow backwardly placed palatine plate. In most Mammals the palatine plate is trun- 
cated anteriorly to form the posterior boundary of the “ anterior palatine foramen ; ” but 
in some, for instance the Pangolin {Manis) and the Hedgehog ( JErinaceus ), the palatine 
plate is sharply wedged-in anteriorly between the dentary and palatine processes of the 
premaxillaries, exactly as in the Fowl (Plate LXXXIY. fig. 6, jp.x., m.x.). The retral 
posterior palatine plates of the Fowl’s maxillaries (maxillo-palatines of Huxley) are 
very thin, scarcely reach the vomer (v.), are fibrous, and are less developed than in any 
family except the Picinse, where they only just appear mesiad of the inner edge of the 
palatine (see Huxley “ On the Classification of Birds,” Zool. Proc. 1867, pp. 448-450, 
figs. 30 & 31, mxp). 
The rest of the maxillary of the Fowl is mere style (a zygomatic process), and ends 
free in the upper lip, having the jugal (j.) mounted on and overlapping it, exactly as in 
those Teleostean Fishes which possess a jugal. 
The jugal (Plate LXXXIY. figs. 6 & 8 ,j.) is similar in form and size to the zygomatic 
process of the maxillary, and is less than the quadrato-jugal (q.j.), which finishes the 
fixing-bar to the quadrate (q.). The quadrato-jugal, like the rest of the facial splints, 
continues distinct from its surroundings. The nasals (fig. 8, n.) overlie the frontal part 
of the ethmoid imperfectly, as in Struthious Birds ; they have a concave semielliptic 
margin anteriorly ; this is bounded by an upper process, which outlies the nasal process 
of the premaxillary, and a descending facial wall-plate, which articulates with the pre- 
maxillary and maxillary below: this lower process is a typically ornithic structure, and 
is aborted in the Struthionidse (see First Paper, Plates vn.-xvi., n.). 
The lacrymal (figs. 6 & 8, l.) has a' large superorbital and a thickish, twisted, ante- 
orbital plate ; these two parts are distinct bones in the Lizard. 
The frontals (fig. 8, f.) are at present very elegant shell-like bones, rounded and smooth 
over the cranium, hollow and scooped over the eye, and having a strong superorbital 
ridge. The thin dentated orbital plate only partly walls-in the orbital fontanelle (of.). 
The oblong, curved, four-sided parietals (figs. 7 & 8, jp.) are overlapped behind by the 
