| OCR Text |
Show 1905.] OSTEOLOGY OF THE EURYLyEMID^E. 43 The quadrato-jugal is long, extending to beyond the middle of the orbit. The vomer is not yet ossified. The palatines differ from those of the adult in that the transpalatine elements (?) are as yet membranous. The pterygoid is rod-shaped, bent at its posterior extremity at an obtuse angle, so as to fit closely to the parasphenoidal rostrum. The free end of this rod is pointed, and bears a small pointed piece of cartilage. Whether this represents the hemipterygoid, or, as seems more likely, the unossified extremity of the shaft, is a point which can only be determined by the examination of somewhat older skulls. The palatine extends backwards beneath these bent limbs of the pterygoid. The apparent absence of the hemipterygoid is a point of considerable interest. The interpretation to be placed upon this fact is, I think, not that the pterygoid shaft retains its primitive integrity, but that the hemipterygoid element has been lost, just as it has in many other groups of birds. My reason for this view is that the vomer, which shows various grades of reduction in the Eurylaemidae, is supported entirely by the palatines, as in all other cases where the hemipterygoid has been greatly reduced or is wanting. There is nothing remarkable in the absence of this element, because, as has been shown, the skull in this group is highly specialised in many ways. The elements of the mandible are as yet distinct. iv. T he V ertebral Column. All the presynsacral vertebrae are heteroccelous and free. The cervical vertebrae are characterised by the deeply incised neural plates of the 6th- 10th vertebrae, where the posterior zygapophyses are borne upon the under surface of the free ends of long beams. The atlas has the odontoid ligament perforated. The axis bears a large tooth-like neural spine and a large pair of hyperapophyses. The second and third have large quadrangular neural plates, the hinder angles of which in the third vertebra are produced upwards into strong hyper apophyses. The outer borders of these plates are pierced, on each side, by a small foramen. The hyperapophyses of the 5th to 8th vertebrae are placed about midway between the neural spine and the posterior zygapophysis. From the 5th to 11th vertebrae the neural plates are deeply incised both before and behind the neural spine. The neural spines gradually decrease in size from before backwards, so that from the 9th to the 12th they are represented only by the merest tubercle. Hypapophyses are borne by the 2nd, 3rd, 4th, and 5th vertebrae; the 7th to 10th bear catapophyses, feebly developed ; hypapo- |
