336 MR. A. H. GARKOD ON THE [•'^P'"' *^» 



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 draw- 

 ing of the vertebrae of the cervical region it is evident that he was 

 not thoroughly acquainted witli the peculiarities of their mutual 

 articulation. 



Eyton t describes briefly the osteology of Plotus novce-hollandice, 

 but does not give figures. The specimen he refers to is in the Col- 

 lege-of-Surgeons' Museum (No. 1179 a). His drawing of P/i«/«cro- 

 corax cristcttusX, however, makes it apparent that he fully realizes 

 the peculiarity of the mutual relationsliips 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. 



h\ speaking of Phalacrocorax crisfatus Mr. Eyton remarks, 

 " The tubercle on the u]jper edge of the occipital bone has a pointed, 

 movable, triangular process attached to it, which I suspect has also 

 been the case witii my 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 «.) 



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 (including the atlas and axis), 

 when articulated together in such a way that all the articular sur- 

 faces 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 ver- 

 tebrae, which are consequently articulated at a considerable angle 



* MImoires de I'Acad. Imp. des Sciences de St. P^tersbourg, torn. v. 6^10* 

 S^rie, Sect. d. Sc. Nat. 1839. 



t Osteologia Avium, p. 218. | Loc. cit. pi. v. f. 1. 



§ Archiv fur Anat. u. Physiol. 1873, p. 357. 



(I Essays and Observations, edited by Prof. Owen (1861), vol. ii. p. 328. 



