| OCR Text |
Show 1895.] LORIUS FLAVOPALLIATUS AND PSITTACUS ERITHACUS. 377 THE DORSAL ASPECT of the cranium (see fig. 3, p. 367) shows, in both species, a surface which is convex both antero-posteriorly and transversely. It is, however, much flattened betw7een the orbits. In L. flavopalliatus there is a slight though marked depression in the hinder part of the interorbital region, which is hardly to be detected in P. erithacus, while in the latter species there may be a median longitudinal depression in the parietal region which does not exist in L. flavopalliatus. In both the dorsal surface of the cranium may be said to be bounded by ten margins. Tbe first or preaxial margin is that which adjoins the prosopium, and is on the whole very slightly concave. The second and third margins (the two preorbital margins) each proceed outwards and postaxiad from one outer end of the first (prosopiad) margin to the preorbital prominence of the same side, and each is about half as long as is the lateral margins of tbe prosopium. The two preorbital margins diverge postaxiad at an angle of about 95° in L. flavopalliatus and of about 80° in P. erithacus. The fourth and fifth margins form the anterior part of each orbital margin (each anterior orbital margin), while the sixth aud seventh margins of the dorsum of tbe cranium constitute the posterior part of each orbital margin (each posterior orbital margin). The anterior and posterior orbital margins meet at a marked angle of about 120°, the apex of which is a little in front of the middle of each orbit's margin. In P. erithacus they run into each other in a curve with only a faint indication of an angle of about 140°, and this is at approximately the middle of each total orbital margin. An axial groove, rather wide and shallow, runs along each side of the dorsum of the cranium within the orbital margin, the two grooves being separated by the moderate transverse convexity of the interorbital region. There is a series of foramina in each groove, which is more marked in P. erithacus than in L. flavopalliatus. The eighth and ninth margins of the cranial dorsum (the two temporal margins) extend from the postorbital prominence to the outer end of the lambdoidal ridge of either side. Each presents a sigmoid curvature, concave behind tbe postorbital prominence and then convex in the squamosal region, external to which the supra-meatal process, the posterior end of the zygomatic process of the quadrate, and the hinder end of the zygoma may appear. The tenth, or occipital, margin presents in both species a gentle convex curvature with a small median concavity. T H E V E N T R A L ASPECT of the cranium exhibits, in both species, a roughly quadrilateral outline, the smallest margin of which is preaxial and corresponds with the postaxial margin of the prosopium. The lateral sides are the longest and coincide with the zygomata (z) and quadrates (q), while the hinder margin is convex and formed by the occiput. The palatines (p) extend forwards much beyond its anterior margin, and each preorbital prominence projects outwards beyond the preaxial third of the zygoma. In the middle of the anterior part of the basis cranii is a rather elongate space, bounded in front by the postaxial margin of the |
