ON THE ANATOMY OF PLOTUS ANHINGA. 335 
left. In Sula bassana, Phalacrocoraz carbo and P. lugubris, Fregata 
aquila, and Phaethon there are two. In Sula fusca (a specimen in 
very bad immature plumage from Port Lemon, Porto Rico) the left 
carotid only exists, as also in Pelecanus rufescens and P. onocrotalus. 
As tothe respiratory organs, from Plate [20] XX VII. fig. 3, it can 
be seen that the syrinx is in no way peculiar, a single pair of intrinsic 
lateral muscles being present. By the side of it I have figured the 
lower portion of the windpipe of a male Gannet (Sula bassana), in 
which a pair of fatty bodies are developed just above the bifurcation 
of the bronchi, the like of which I have not elsewhere seen. 
Osteologically Plotus anhinga. deserves some special attention. Page 336. 
Brandt* in his valuable memoir on avian anatomy has fully described 
and figured the skeleton. Nevertheless from his drawings of the 
vertebre of the cervical region it is evident that he was not thoroughly 
acquainted with the peculiarities of their mutual articulation. 
Eytonf describes chiefly the osteology of Plotus nove-hollandie, but 
does not give figures. The specimen he refers to is in the College-of- 
Surgeons’ Museum (No. 1179 a). His drawing of Phalacrocoraz 
cristatust, however, makes it apparent that he fully realizes the pecu- 
; liarity of the mutual relationships of the cervical vertebre of 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 pecu- 
larity 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 Phalacrocoraz 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 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 
superficial temporal muscles meeting behind the skull along the median 
* “Mémoires de Acad. Imp. Sciences de St. Pétersbourg,” tom. v. 6&™= Série, 
Sect. d. Se. Nat. 1839 
+ “Osteologia Avium,” p. 218. t Loc. cit. pl. ¥. £.1. 
§ “Archiv. fiir Anat. u. Physiol.,” 1873, p. 357. 
|| “ Essays and Observations,” edited by Prof. Owen (1861), vol. ii. p- 328. 
