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Show 1895.] LORIUS FLAVOPALLIATUS AND PSITTACUS ERITHACUS. 379 prosopium and laterally, and also postaxially, by the palatines. The anterior and larger portion of the roof of this space is formed by the postpalatal ventral surface of the prosopium; behind the hinder margin of this surface it is roofed by the basis cranii. This part of the ventral surface of the cranium shows in L. flavopalliatus a median, triangular raised surface narrowing backwards and traversed antero-posteriorly by a slightly marked ridge. Externally this surface is a groove widening backwards, with a perforation at its hinder end for the olfactory nerve. Postaxially each of these fossae is Hmited by a transverse ridge-the crucial ridge (figs. 9 & 10, cr). Beneath the anterior part of the fossa a sharp uncinate process projects inwards, and, at its apex, somewhat backwards. In L. flavopalliatus the dorsal portion of each palatine is bent mesiad to meet the corresponding part of the other palatine much more sharply than in P. erithacus, so that when the basis cranii is looked at these bent-in portions of the two palatines present a considerable extent of flattened surface almost equalling that of the hinder margin of the bony palate between the two palatines. Moreover, each bent-in part forms internally almost a right angle with the vertical main portion of the bone, while externally (or dorsally) the angle is yet more marked. In P. erithacus each palatine gently curves to meet its fellow, so that there is hardly any ventral flattened surface, while internally the median part forms a very obtuse angle with the vertical main portion of the bone, though externally (or dorsally) the angle is very marked and the dorsal surface is flattened and transversely concave. Thus tbe inner and outer surfaces of the palatine correspond in neither species. From the inner end of the anterior margin of each palatine an anterior palatine process l extends forwards beside its fellow of the other palatine. These are less marked in P. erithacus, and they are not side by side but diverge more forwards, so leaving a greater gap between them. On the other hand, this species has (as before mentioned) long posterior palatine processes which are wanting in L. flavopalliatus. In the latter there are two postaxial processes, one on side of the posterior end of the mid-junction of the palatines, so that the postaxial margin of the two conjoined palatines presents three concavities instead of only one as in P. erithacus, though a delicate styliform process extends backwards from the ventral and inner surface of each palatine to beyond its postaxial margin. In both species the pterygoids (pt) diverge from the middle of the hinder margin of the palatines and the rostrum of the basis cranii, with which latter, however, they do not articulate. The palatine, the pterygoid, and the zygoma of each side bound a triangular space wherein is seen the roof of the orbit. The great olfactory opening is hidden (in this view) by the palatines. In the front of each of these triangular spaces is seen the junction of the prosopium with the cranium and the part behind it (just described), only the crucial ridge is almost entirely concealed by 1 See above, p. 375, the first three lines. |