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Show 1902.] OSTEOLOGY OF THE FALCONIFORMES. 293 hyperapophyses are particularly well developed. The 2nd to 4th vertebrae bear hypapophyses: beyond these they are replaced by catapophyses, which near the cervico-thoracic vertebra again give place to hypapophyses. These catapophyses never coalesce to form a carotid canal. In many of the larger- Accipitres the cervical vertebrae from say the 5th to the 8th have the neural plate deeply excised posteriorly, so that the postzygapophyses appear, each as an articular facet at the extremity of a long beam. The ventral surface of the centrum is either flattened or slightly grooved. There is a very close similarity between the cervical vertebrae of the Accipitres and the Striges: so close is this resemblance that the one is hardly distinguishable from the other. The chief differences appear to be in the fact that the cervical ribs of the Striges are relatively slightly longer- and the catapophyses somewhat more sharply defined. The pleurosteal lamella is also somewhat more band-like and sharply defined. The hyperapophyses of the axis are abruptly trirncated in the Owl, tubercular in the Accipitres. For the rest, the differences are not greater than those which normally obtain between species or genera, at most. The cervici-thoracic vertebrae may be two or three in number. The thoracic vertebrae, as already remarked, are free save in the Falconidse and Polyboriclse. W h e n free, they may be distinguished from those of the Strigidse in that the neural spines are relatively lower, wider antero- posteriorly, and not markedly inclined forward. Hypapophyses in the Strigidse do not extend beyond the second vertebra: in the Accipitres with free vertebrae to the third. In the Strigidse there may be a large pneumatic aperture between the articular surfaces for the capitulum and tuberculum, and a second caudacl of this. As in the Accipitres so in the Striges, each transverse process sends forward and backward a long slender spike from its extreme lateral border; each spike overlaps similar spikes from the vertebra next in front and behind it. The neural spines may also send backwards from the upper border a pair of short spike-like processes, to embrace the neural spine immediately behind it. In Serpentarius the thoracic vertebrae, from the 2nd to the 5th, are pierced by a large pneumatic foramen, opening at the base of the neural spine immediately behind the anterior zygapophysis. This leads into an extensive chamber, excavated out of the vertebral tissue and extending down to the spinal cord, being-separated therefrom only by a thin plate of bone. Other pneumatic apertures pierce the lateral walls of the neural tube, and the centrum below this. In the majority of the Accipitres, the pneumatic apertures of the thoracic vertebrae are restricted to a single opening at the base, and caudad of the transverse process and immediately in front of the base of the postzygapophysis. In the Cathartse the apertures are three in number, and lie on |
