OCR Text |
Show 374 DR. ST. GEORGE MIVART ON THE SKELETON OF [May 7, in L. flavopalliatus both these margins run indistinguishably one into the other in one continuous curve. In both species the ventral margin of the quadrate is convex in both directions, corresponding with the elongated articular groove of the mandible. A second articular surface1 for the mandible (one which articulates with the inner surface of the articular process of the latter) is situated on the hinder part of the external surface of the quadrate behind and below the externally extending zygomatic process. This surface is strongly concave from without inwards and slightly convex in the opposite direction. The anterior margin of the quadrate has a short, anteriorly concave outline where it joins the pterygoid (pt), dorsad of which is a very sharp-pointed process (the orbital process) extending forwards, inwards, and somewhat dowoiwards from just below and in front of the base of the ascending process (see, in fig. 1, the process ascending above the hinder end of tbe zygoma, and, in fig. 2, above that of the pterygoid). The zygoma, though nearly straight in both species, is slightly more bent concave dorsally for about its middle third in L. flavopalliatus. It is also, even relatively, somewhat more slender, and does not expand dorso-ventrally where it joins the prosopium nearly as much as in P. erithacus. Apart from this expansion the zygoma is throughout of nearly tbe same dorso-ventral and transverse extent in each species. As before said, the sphenotic process does not so nearly touch the zygoma in L. flavopalliatus; yet though it is thus relatively shorter, the lachrymal process approaches it much more nearly, diverging very slightly therefrom as it arches backwards, a little outwards, and subsequently upwards. The distance between its apex and that of the sphenotic process is not more than half the distance from the apex of the sphenotic process to the quadrato-zygomatic articulation, while in P. erithacus it nearly equals that distance. The lachrymal narrows very gradually to its apex. This narrowing is more gradual in L. flavopalliatus, which also has the apex more truncated aud the dorsal margin of the whole process more strongly concave upwards owing to its greater prolongation postaxiad. The outer surface of the cranium in the lachrymal region in front of the orbit is smooth. The lachrymal is very convex dorso-ventrally down to a point nearly opposite the supra-jugular process of the prosopium. Then it becomes concave in that direction iu both species, but the concavity is very marked in L. flavopalliatus, assuming tbe form of an antero-posteriorly directed groove, sharply limited above and below. In P. erithacus the same groove exists, but it is very much less marked. Beyond this groove the lachrymal is very slightly convex dorso-ventrally in P. erithacus, while in L. flavopalliatus it presents a more decidedly flattened surface which looks outwards and somewhat downwards. The postero-superior margin of the palatine is, in both, connected with the basis cranii for rather less than half that margin's extent, 1 See below, p. 391. |