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Show 1895 ] LORIUS FLAVOPALLIATUS AND PSITTACUS ERITHACUS. 381 the same transverse line, while the two external ones probably answer to the lateral ends of the M-like ridge of L. flavopalliatus because a vagal foramen opens just above each of them. In this species there is on either side of the cranium a roughly quadrilateral space bounded anteriorly by the outer end of the posterior transverse basi-temporal ridge, internally by the lateral margin of the foramen magnum, externally by the paroccipital process, and posteriorly by a rounded prominence (exoccipital prominence) running from the summit of the side margin of the foramen magnum to the posterior surface of the paroccipital process. In P. erithacus the conditions are similar save that the exoccipital prominence is somewhat less pronounced and ridge-like. In both species a foramen opens on the exoccipital prominence about midway between the margin of tbe foramen magnum and the base of this paroccipital prominence, but this foramen is larger and very much more conspicuous in L. flavopalliatus. The side of the paroccipital process bounding this quadrilateral space (the inner aspect of the process) has in both species a conspicuous foramen opening into it. The infero-external aspect of this process is very different in the two species. In L. flavopalliatus it is wide, strongly concave transversely, and looks mainly downwards. In P. erithacus it is but slightly concave transversely and looks more outwards. The posterior end of the paroccipital process in L. flavopalliatus is bent more sharply backwards than in P. erithacus and also somewhat inwards (see figs. 1 & 2 and 9 & 10). The basi-temporal shield is limited laterally by two very sharply raised ridges, which meet together just below the eustachian aperture and end in a median sharp-pointed process projecting forwards beyond and beneath it (fig. 6, me). Between its lateral and postaxial ridges the shield is smooth and slightly concave, without ridges or foramina. In P. erithacus its lateral ridges are much less well-defined and are represented by two slightly elevated prominences each of which is marked by a very narrow longitudinal groove, but the shield also ends medianly in front in a pointed eustachian process (me) projecting forwards beneath the eustachian opening. The surface of the shield is slightly undulating, and a little behind the eustachian process is a depression behind which there may be a median ridge. In L. flavopalliatus there is outside each lateral basi-temporal ridge a wide transverse concave surface which becomes continuous posteriorly with the ventral surface of the paroccipital process. It is bounded superiorly and externally by a slight ridge running forwards and inwards from just below the foramen ovale and ending in a small preaxiad process-the lateral eustachian process (tig. 6, le). In P. erithacus this concave surface is narrower and does not approach so nearly the foramen ovale, while the ridge bounding it superiorly and externally ends in a more marked lateral eustachian process (fig. 7, le). |