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 re- 

 curved 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 opportunit}' 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 *. 



The antorbital plate, or the " pars plana," is an enormously enlarged 

 mass of bone, which has inclistinguishably 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 ]josteriorly. 

 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 ew 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. 



