Vol. XII. 



1 Shufeldt, Osteology of Ccreopsis iiouic-liolldtidice. 21 1 



being concaved posteriorly on either side of the middle line of 

 the skull.* 



Quite different from Chlocphaga hybrida is Chlocphas;a polio- 

 cephala in this respect, for in it the supra-orbital depressions 

 are shallow, rather far apart, and little more than narrow 

 trimmings of the supra-orbital peripheral margins, as far forwards 

 as the articulation of a lacrymal bone on either side. (Fig. 4, 

 PI. XXVIII.) These depressions are still less conspicuous in species 

 of the genera A user, Chen, and Br ant a, while in C. juhata they 

 are slightly more evident, Init very narrow. Hymenolcemus 

 malacorhynchiis has them not at all, and Tachycres cinereiis has 

 them extensive, but very shallow, though in this bird they give 

 rise to an evident mesial crest, extending from the frontal region 

 backward to the parietal. 



None of the foregoing among the Geese possesses any movability 

 to the " cranio-facial hinge." It is absolutely rigid in all save 

 Chlocphaga hybrida, in which species, in the case of the skull 

 before me, it is perfect (No. 1,820, Coll. U.S. Nat. Mus.). 

 Nevertheless, the transverse line of the suture in this region 

 usually persists throughout life in all these forms, and in most of 

 them, in the middle line in this region, we may discern the sutural 

 traces of the naso-frontal processes of the premaxillaries. 

 Exceptions to this are to be seen in Branta c. hutchinsi (No. 7,357, 

 Coll. U.S. Nat. Mus.), and they are very faint in Ccreopsis. (Fig. 18, 

 Plate XXX.) 



Taken in its entirety, the superior inandibuhir portion of the 

 skull exhibits a very considerable amount of variation in the 

 several genera of Geese to which I have referred in the foregoing 

 paragraphs. As may be observed by examining the several 

 figures on the plates, in Ccreopsis novce-hollaiidicc this facial part 

 of the cranium is relatively short, while, at the same time, it is 

 markedly broad and deep. Either external narial aperture is 

 broadly elliptical and of great size — so large, indeed, that the 

 naso-premaxillary part of the superior mandible above them 

 is mounded up, more or less convex, externally, and is unusually 

 wide, transversely, between these narial apertures. This elevated 

 portion slopes down in front, more or less abruptly, a short 

 distance behind the broadly-rounded termination of the superior 

 mandible (fig. i, Plate XXVIII.), the terminal area, superiorly, 

 showing the usual scattered group of nutrient foramina. 



Laterally, the tomial margins are both sharp and deep, and the 

 osseous roof of the mouth between them is profoundly concaved. 

 Mesially, this latter may exhibit a small, slit-like foramen, which, 

 in some Geese, is of elliptical outline and of great size, as in 

 Tachycres cinercus. Where small, the roof of the mouth is nearly 



* Shufeldt, R. W., "Contribution to the Study of the 'Tree-Ducks' of 

 the genus Dendrocygna." Plate XI., fig. 35 (in MS.) This memoir, when 

 published, will, on thirty-five plates, give figures of skulls and other parts 

 of the skeleton of a large number of the Anseres from various regions of the 

 world. 



