OCR Text |
Show 1902.] OSTEOLOGY OF THE FALCONIFORMES. 289 In all the desmognathous palates the maxillo-palatine processes remain free posteriorly. In the Cathartse we have a palate of quite peculiar1 type (PI. X X X I . fig. 1). The maxillo-palatines, as in Elanus, are relatively small. But whilst, in Elanus, it will be remembered, they were of a spongy texture, in Cathartse they are represented by a shell-like lamina with its concavity downwards. The external lateral border- of this lamina is anchylosed with the nasal. The antrum is represented by a small cavity at the extreme anterior extremity of the plate. These shell-like laminae fail to meet in the middle line ; nevertheless the palate must be regarded as of the indirect desmognathous type on account of the fact that the nasal septum expands ventrally into a horizontal plate, fusing on either side with a pair of strap-shaped laminae arising from the inner dorsal border of the maxillo-palatine processes (=the anterior septo-maxillary spur, Parker). Distad of the maxillo-palatines and nasal septum is a large anterior palatal vacuity roof ed only by the nasal processes of the premaxilla. This region of the jaw recalls that of the Tubinares. But the palate of the Tubinares differs in the absence of an ossified nasal septum and the great size of the vomer. The jugal is wanting from the quadrate-jugal arch in the Falcons. It is certainly present in Accipiter, and perhaps in other Accipitres. In some examples of Hierofalco the quadrate-jugal bar is connected with the maxilla by a distinct joint. The maxilla contributes towards this articulation a backwardly directed, columnar bony process, which immediately overhangs the extreme posterior angle of the tomium. Seen from below, the articulation is transverse in form. From above, it is concealed by a spike of bone from the quadrato-jugal, which projects forwards into the mouth of the antrum. The sporadic formation of a joint in this position seems to m e a point of some considerable interest. The Vomer, Palatine, and Pterygoid, The vomer in the Accipitres is never a very large bone. It is blade-shaped when completely developed, and sometimes is slightly bifurcated at its extreme posterior end--seen from the ventral surface. Its base is received between the anterior borders of the dorsal laminae of the posterior expanded end of the palatine: sometimes fusing therewith, e. g. Serpentarius. In the Falcons the vomer terminates in a bilobate expansion which rests upon the fused maxillo-palatine processes, between their free posterior projections. In Polyborus and Milvago this expansion is barely perceptible. In Milvus (e. g. M. ater), Hcdiastur, Pernis, and Buteo (e. g. B. jakcd) the vomer is long and slender, and anchyloses with the maxillo-palatines. In Aquilince the vomer extends far forwards between the maxillo-palatines, but remains perfectly distinct therefrom. |