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Show 336 MR. A. H. GARROD ON THE [^Pr' **^» Osteologically Plotus anhinga deserves some special attention. Brandt * in his valuable memoir on avian anatomy has fully described and figured the skeleton. Nevertheless from his drawing of the vertebras of the cervical region it is evident that he was not thoroughly acquainted with the peculiarities of their mutual articulation. Eyton f describes briefly tbe osteology of Plotus novee-hollandice, but does not give figures. The specimen he refers to is in the Col-legc- of-Surgeons' Museum (No. 1179 A ) . His drawing of Phalacrocorax cristatus J, however, makes it apparent that he fully realizes the peculiarity of the mutual relationships of the cervical vertebrae in its close allies. W . Donitz§ draws attention to a peculiarity in the cervical region of Plotus levaillantii which will be referred to further on. This peculiarity is not represented in Brandt's figure of P. anhinga ; and it is not to be found in either of the Society's specimens, one being at least three and a half years old. In speaking of Phalacrocorax cristatus Mr. Eyton remarks, " The tubercle on the upper edge of the occipital bone has a pointed, movable, triangular process attached to it, which I suspect has also been the case with m y specimen of Plotus, but has been lost." In the Society's female specimen there is a fibro-cartilaginous similarly situated process, not more than one sixth of an inch long, which is ossified in the evidently older male. In his notes on the anatomy of the Cormorant, Hunter tells us || that "a small bone, about an inch long, passes back from the os occipitis and gives origin to the temporal muscle, which is very strong." The same bone in the Darter, although comparatively not so long, performs the same function, the superfical temporal muscles meeting behind the skull along the median raphe, which becomes ossified to form the above-mentioned bony style in the adult bird. (See Plate XXVIII. fig 1 a.) Before commencing the description of the cervical articulations of the Darters, it may be mentioned that the same condition is observed, only in a less marked degree, in the Cormorants, and still less in the Gannets and Pelicans. The first eight cervical vertebrae (iucluding the atlas and axis), when articulated together in such a way that all the articular surfaces are in their proper relations one to the other, form a continuous curve with a strong concavity forwards. So considerable is this curve, that when the beak of the bird is horizontal the axis of the peculiarly long eighth vertebra is parallel to that of the skull, or very nearly so. The curve is not a part of a circle, but is one which gradually augments in acuteness from above downwards, its most considerable development being between the 7th and 8th vertebrae, which are consequently articulated at a considerable angle * Memoires de l'Acad. Imp. des Sciences de St. Petersbourg, torn. v. 6&m« Serie, Sect. d. Sc. Nat. 1839. t Osteologia Avium, p. 218. J Loc. cit. pl. v. f. 1. § Archiv fiir Anat. u. Physiol. 1873, p. 357. |) Essays and Observations, edited by Prof. Owen (1861), vol. ii. p. 328. |