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Show 304 PEOF. T. W. BEIDGE ON THE [Apr. 2, As far as could be seen in the dried skull, the usual connection between the anterior extremity of the palato-pterygoid bar and the lateral ethmoid of its side must have been of a loose ligamentous character. Between the metapterygoid and the parasphenoid there is a singular articular connection. From the antero-superior angle of the metapterygoid a process (fig. 3, mt.a.) is bent inwards towards the base of the skull and lies in the horizontal plane. The anterior and posterior margins of the process are curved slightly upwards in such a way that the process forms a somewhat shallow, demi-cylindrical, articular surface, the concavity of which looks directly upwards. The mesopterygoid (figs. 3 and 4, mp.g?), which, as already mentioned, overlaps the inner surface of the metapterygoid, is also bent horizontally inwards, but at its postero-superior angle, and, moreover, partially embraces the preceding process in such a way as to strengthen the floor and, at the same time, deepen the sides of the demi-cylinder. The hyomandibular also contributes to the formation of this curious articular surface. A process2 from the anterior margin of the superior half of that bone (fig. 3, hym.1) is prolonged obliquely downwards and forwards, and, after blending with the anterior lip of the demi-cylinder, becomes applied to the adjacent upper margin of the mesopterygoid (m.pg.). It will be seen, therefore, that this process not only strengthens the anterior wall of the demi-cylinder, but, in addition, furnishes the latter with an incomplete roof. In the normal condition of these parts the articular processes of the parasphenoid fit into the two demi-cylindrical articular surfaces provided for them by the meta-pterygoids, in such a way, that a lateral sliding motion of the latter on the parasphenoid is possible. In addition to the acutely-pointed teeth in the premaxilla?, maxillae, and vomers, both the mesopterygoid and pterygoid bones carry teeth of variable size over nearly the whole extent of their inner or oral surfaces. The inferior border of the pterygoid (fig. 3, pg.) carries a series of small pointed teeth arranged parallel to the more externally situated and larger maxillary teeth (mx.). The rest of the inner surface of the bone (fig. 4, pg.) exhibits a granular appearance, from the presence of numerous, extremely fine, closely-set teeth. For the same reason the greater part of the oral surface of the mesopterygoid (m.pg.) has a very similar appearance, but, within a short distance of the superior margin of the bone, the fine denticles are replaced by a single longitudinally disposed row of much larger, conical, pointed teeth (fig. 4). Of these teeth the most posterior are the largest, and, moreover, are situated exactly opposite the mesial cluster of teeth in the parasphenoid; from this point forwards the teeth gradually but rapidly diminish in size. The teeth are slightly curved, and hence their pointed enamel-tipped crowns are directed obliquely inwards and a little downwards towards the corresponding teeth of the 2 I a m inclined to think that this process is not an actual extension of the hyomandibular, but, on the contrary, is really an ossified ligament. |