OSSEOUS SYSTEM OF AVES. 59 



it is longer and more slender. In Casuarius the lacrymal coalesces 

 with the frontal, prefrontal, and nasal, but retains its freedom 

 in other StruthionidcB. The lacrymal is very large in Dacelo 

 and Ti'ochilus, fig. 18, Z. 



The skull in the Raj^tores, 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 occipital foramen 

 is almost horizontal. The superoccipital muscular depressions are 

 well defined. The temporal fossa3 are not very deep, and are 

 wide apart superiorly. The cerebral convexities are not strongly 

 marked; the frontal region is flat. A longitudinal furrow 

 extends along the whole upper surface of the cranium in some 

 Owls. 



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, from the size of the lacrymal bone and 

 of the transverse lamina of the prefrontal ; the internal and pos- 

 terior orbital parietes are defective ; the optic foramina are com- 

 monly blended into one, and continuous vvith the larger fissures 

 above. 



In the Parrots the upper surface of the cranium is flattened or 

 slightly convex, and greatly extended in breadth between the 

 orbits for the articulation of the naso-premaxillary bone, fio-. 

 30, n. 



In the Toucans the cranium slightly increases 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 surface, which 

 is absolutely concave in the Macaws, from the backward exten- 

 sion of the paroccipitals, is slightly convex in the Toucans, where 

 it is separated from the upper surface by a regularly arched ridge. 

 The cerebellar prominence extends over the occipital foramen, the 

 plane of which inclines forward and downward from the horizontal 

 line at an angle of 45°. The circumference of the orbit is un- 

 inclosed by bone at the posterior part, the postorbital processes 

 of the frontal not being developed as in most Parrots. The 

 septum of the orl^its is very incomplete. The nostrils open on the 

 posterior part of the upper mandible, which presents a smooth 

 entire surface formed by the thin parietes of the dilated cellular 

 osseous tissue. 



In the Helmeted Hornbill (Buceros galeatus) the outer sur- 

 face of the skull is sculptured with irregular furrows and risings,^ 



