AVES. 



279 



cave or flattened. Anterior to this part the 

 cranium in the Parrot presents the moveable 

 junction of the upper mandible, but in other 

 birds a continued osseous surface converges 

 more or less gradually to the end of the beak, 

 only interrupted by the anterior orifices of the 

 nasal cavity. 



The skull in the Raptores, especially in the 

 nocturnal division, is short, broad, and high, in 

 proportion to its length, and the cranium is 

 large compared with the face. The posterior 

 facet is convex, and remarkably extended up- 

 wards and laterally, and is continued insensibly 

 at an obtuse angle with the upper surface. 

 The occipital foramen is almost horizontal. 

 The temporal fossse are not very deep, and do 

 not meet above at the middle line. The cere- 

 bral convexities are not strongly marked ; the 

 frontal region is flat. A longitudinal furrow 

 extends along the whole upper surface of the 

 cranium, and is especially remarkable in the 

 Owls. The cranium and face are separated by 

 a sudden contraction. The orbits are very 

 complete, on account of the development and 

 complete junction of the frontal, ethmoidal, 

 ungueal, and palatine boundaries. 



The cranium of the Warblers presents a 

 more regular sphericity, but the interorbital 

 space is very concave. The anterior parietes 

 of the orbits are large and very complete from 

 the size of the lachrymal bone and of the trans- 

 verse lamina of the ethmoid ; the internal and 

 posterior bony parietes are, on the other hand, 

 remarkably defective; the optic foramina are 

 indeed commonly blended into one, and con- 

 tinuous with the larger fissures above. 



The distinctive characters of the skull of the 

 Scansores are the most remarkable, especially 

 in the Parrots and Toucans. In the former 

 the upper surface of the cranium is flattened or 

 slightly convex, and greatly extended in breadth 

 between the orbits. These cavities are very 

 complete ; and the nasal inlets on the sides of 

 the skull are much limited in size by the extent 

 of ossification. However, the breadth of the 

 posterior part of the base of the cranium and 

 the large size of the pterygoid bones occasion 

 a very considerable interval between these and 

 the body of the sphenoid. 



In the Toucans the cranium slightly in- 

 creases in breadth to the anterior part where it 

 is joined to the enormous bill. Its superior 

 surface presents an equable convexity. The 

 temporal fossae, like those of the parrots, are 

 small, and wholly confined to the lateral 

 aspects of the cranium. The posterior sur- 

 face, which is absolutely concave in the Mac- 

 caws, from the backward extension of the 

 mastoid processes, is slightly convex in the 

 Toucans, where it is separated from the upper 

 surface by a regularly arched ridge. The 

 cerebellic prominence extends over the occi- 

 pital foramen, the plane of which inclines 

 forwards and downwards from the horizontal 

 line at an angle of 45. The circumference 

 of the orbit is uninclosed by bone at the pos- 

 terior part, the postorbital processes of the 

 frontal not being developed as in the parrots. 

 The zygomatic process of the temporal, with 



the ligament extending between it and the 

 malar bone, forms here the posterior boundary 

 of the orbit. The septum of the orbits is very 

 incomplete. The ungueo-maxillary fissure and 

 the external nasal apertures are very small, 

 arid situated on nearly the same perpendicular 

 line, the nostrils open on the posterior part 

 of the upper mandible, and the remainder of 

 the lateral facet is, therefore, a smooth entire 

 osseous surface formed by the thin parietes of 

 the dilated cellular mandibles. 



In the Hornbills the skull presents the same 

 characters as in the Toucans, with the exception 

 of that extraordinary species the Helmeted 

 Ilornbill ( Buceros Galeatus.) In this bird the 

 whole outer surface of the skull is sculptured 

 with irregular furrows and risings, a character 

 which it presents in no other bird, and which 

 can only be compared to the surface of the 

 skull in the Crocodiles. The posterior surface 

 is concave, and separated by a strongly deve- 

 loped ridge from the temporal furrows, which 

 almost meet at the vertex. The bony rim of 

 the orbit is completed by the extension of the 

 zygomatic process of the temporal to that of 

 the malar bone, which, however, are not an- 

 chylosed, but joined by a ligamentous union. 

 The bony septum of the orbits is complete, and 

 formed by two strong plates, separated by an 

 intermediate cellular diploe, except at the pos- 

 terior part. The optic foramen is directed 

 transversely outwards. In all the Hornbills 

 the malar bone is moveably connected with the 

 maxillary as well as the tympanic bones, as in 

 other birds. 



In the Wood-peckers the cranium is round- 

 ed, the temporal fossae shallow, the internal 

 wall or septum of the orbits incomplete, but 

 the anterior boundary is well developed. The 

 posterior facet of the cranium is raised. The 

 superior surface is traversed by a wide furrow 

 extending longitudinally forwards, generally to 

 the right, but sometimes also to the left, as far 

 as the lachrymal bone. It is in this furrow 

 that the elongated cornua of the os hyoides are 

 lodged, which relate to a peculiar mechanism 

 hereafter to be described. In some of the 

 larger species of Wood-pecker, as the Picus 

 major, L. the cranial furrow is more symme- 

 trical. In the Humming-birds it is double, the 

 hyoidean furrows being separated at first by the 

 cerebellic protuberance, and afterwards by a 

 mesial longitudinal ridge. 



The skull in the Rasorial birds is narrow, 

 but slightly raised, and without ridges. In 

 the Capercailzie (Tetrao Urogallus) it is 

 almost square, flattened on the posterior and 

 superior surfaces, and impressed with a con- 

 siderable longitudinal furrow anteriorly. The 

 orbit is very incomplete, the anterior pa- 

 rietes being almost entirely wanting, and the 

 ungueo-maxillary vacancy being consequently 

 continuous with the orbit. In the Bustards 

 the posterior boundary of the ungueo-maxillary 

 fissure is complete, but in other respects the 

 cranium resembles that of the Rasores. 



The skull is remarkable for its length in the 

 majority of the Waders. In the Herons and 

 Bitterns the occipital region is low, and inclines 



