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Show 1891.] SAUROGNATHISM OF THE PICI. 127 They may come to the posterior margin of the right external narial aperture. They may hardly come up on the cranium at all. Whenever they do, the cranium is usually externally furrowed to receive them. 22. Sclerotal plates of the eye commonly fuse completely together around their external periphery and towards the centre. 23. " Double ' infrastapedial' and ossified stylohyal" (Parker). 24. Rings, semirings, and other parts of the trachea ossify. 25. There are 19 free vertebrae between the skull and pelvis : the vertebrarterial canals pierce the atlas, and in some species the axis ; the atlantal cup is perforate ; there are no parial parapophyses ; the carotid canal m a y or m a y not be entirely closed in by bone ; where they are present the neural and haemal spines are usually very large. There are three pairs of cervical ribs, five pairs of dorsal ribs, and one pair of sacral ribs. The haemapophyses of the latter do not reach the sternum. In some species the first pair of costal ribs are very robust, as are the last pair of cervical ones. There are five or usually six tail-vertebrae (free), with an enormous pygostyle. Most of these parts are highly pneumatic. 26. The sternum is 2-notched on either side of the carina ; the manubrium is either slightly or very much bifurcated; the costal processes are long and pointed, and the keel is usually rather shallow, projecting forwards and carried up under the mauubrial process. The sternum is usually completely pneumatic. 27. In the pelvis we find the ilia gradually diverging from the sacral crista as they pass forwards. Parial interdiapophysial foramina are either very minute or entirely absent. Ischial notch on the posterior margin of the bone long, rounded, and shallow. Acetabulae large, and bases completely absorbed. Sides of pelvis usually very deep. Postpubis slender, extends beyond ischium, the foot of which latter may or m a y not fuse with it. Obturator space large, and may or m a y not merge with the obturator foramen. Three of the vertebrae of the sacrum anteriorly throw out their processes agaiust the ventral iliac walls. The pleurapophysial and transverse processes of the sacral vertebrae opposite the acetabulae are not modified and lengthened so as to act as braces at the points in question. The pelvis is commonly completely pneumatic. 28. Bones of the shoulder-girdle pneumatic, with the exception (sometimes) of the furcula. This latter is of the U-shaped pattern, without hypocleidium, large, flat scapulo-coracoid ends (which originate from separate ossific centres in the young), and with laterally compressed limbs. Posterior end of scapula more or less modified to be bent or to curl outwards, giving the bone a very unique form. Coracoids long, not very stout, aud with the anterior end more or less laterally compressed. 29. A n os humero-scapulare present at either shoulder-joint; functional, and has m u c h the same shape as the ossicle has in the Passeres. 30. Either the humerus alone, or it together with the long bones of the antibrachium, may be pneumatic. A s nail sesamoid is found at |