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Show 888 DR. R. W. SHUFELDT ON THE OSTEOLOGY OF THE [Dec. 1, The lacrymo-frontal region is very broad transversely in Trochilus, and presents a deep and well-defined triangular depression in the median line, with its apex directed to the front. Posterior to this the vault of the cranium mounds up, smooth and semiglobular. A median furrow marks this part of the skull, which divides behind, to have its branches pass on either side of the supraoccipital prominence forming its lateral boundaries. In life these creases lodge the recurved and delicate extremities of the hyoidean apparatus. The superior orbital peripheries are somewhat tilted upwards in this skull, for their posterior moieties (fig. 1). In the side view, as shown in fig. 2, the peculiar conformation of the superior mandible is still better seen. This aspect also affords us a good opportunity to see the position of the vomer Vo, and its relation to the surrounding bones. A nasal is a delicate and quite straight bar of bone, which descends at an angle of about 45° to meet the usual elements below and merge into them. Above, it forms the rounded posterior margin of the narial opening, thus constituting the holorhinal type of structure as described by Mr. Garrod 1. The antorbital plate, or the "pars plana," is an enormously enlarged mass of bone, which has indistinguishably incorporated with it the lacrymal. This extraordinary development may be seen in all of the views of the skull of Trochilus which illustrate this paper, and its form easily studied. Anteriorly, it is convex from above downwards, being correspondingly concave in a similar direction posteriorly. Above, it rises to a greater height than the margin of the orbit, while below it rests upon the maxillary and jugal bar. Its lateral extension is nearly equal to that of the brain-case behind. Now although this gives to the anterior wall of the deeply excavated orbit a nearly unbroken surface, being pierced alone by a minute foramen for the passage of the olfactory nerve, it is more than can be said for its posterior surface, which latter is almost completely deficient in an osseous partition separating the orbital cavity from the brain-case. This deficiency is so far extended forwards as to include the hinder portion of the interorbital septum. It will be seen by referring to fig. 2 that this latter is of very limited extent, as the lower notch there shown denotes the point where the optic nerve issues from the cranium. With the exception of a minute span of bone behind, the groove that lodges the olfactory nerve on its passage through the orbit is an open one, and leads directly to the foramen in the pars plana, already described. The quadrate of this Hummer is an exceedingly curiously formed bone, while its method of articulation is equally unique among birds, so far as I am aware, being extended, when in situ, nearly in the horizontal position between its mastoidal and quadrato-jugal articulations. Its mandibular foot presents for examination two transverse and very narrow facets, a similar number being awarded to its mastoidal 1 P. Z. S. 1873, pp. 33-38. |