198 
GENERAL ORNITHOLOGY. 
and are termed aves Icevo-carotidmce (fig. 91). 3. In certain parrots only, with two carotids, 
the right is as in (1), but the left runs superficially along the neck with the jugular vein and 
pneumogastric nerve; such birds are aves hicarotidincB ahnormdles (fig. 92). 4. Two carotids, 
arising normally, unite almost immediately, and the single trunk runs to near the head, just as 
if there were two as in (1); then it bifurcates, as in birds with left carotid only (2). Such birds 
are termed aves conjuncto-carotidince. Special cases of (4) are : in the bittern, the two roots 
are of nearly equal size (fig. 93) ; in the flamingo, the left is very small (fig. 94) ; in a cockatoo, 
the right is very small (fig. 95). Parrots display all four of the arrangements ; the cases of the 
bittern and flamingo are unique. The question is thus for nearly all birds narrowed to whether 
there be two normal carotids (1), or the left only (2). Observations upon three hundred genera 
show two in one hundred and ninety-three, in one hundred and seven the left only ; but the 
Fig. 93, Fig, 94. Fig. 95. 
Figs. 90-95. — Diagrams of carotid arteries of birds : h, root of aorta ; a, arch of aorta, to the right side ; li, left 
innominate ; ri, right innominate ; Is, left subclavian ; rs, right subclavian; Ic, left carotid; rc, right carotid. (1) 
Fig. 90. Aves bicaroiidince normales, with two carotids, both alike. (2) Fig. 91. Aves Icevo-carotidince, with left 
carotid only. (3) Fig. 92. Aves bicarotidince abnormales, certain parrots, with two carotids, not alike. (4, 5, G) 
Aves conjuncto-carotidince, with two carotids, which speedily unite in one. (4) Fig. 93, bittern, both alike. (5) 
Fig. 94, flamingo, left very small, (6) Fig. 95, cockatoo, right very small. (Copied by Shufeldt from Garrod.) 
numerical proportion of Passerine genera makes (2) the most frequent arrangement. There is 
but one carotid in all Passeres as far as known ; in most Cypselidce ; in Trogonidce, Meropidce, 
Upupidce, RhamphastidcB, some Psittad, the Turnicidce, Megapodidce, Podidpedidce, Alcidae, 
Rheidce, Apterygidce. Thus in Passeres, ColumbcB, Accipitres, Grallce, and Anseres, the 
carotid arrangement is an ordinal character, all but the first named of these great groups 
having two. The character separates most of the families of Picarian" birds, and also dis- 
tinguishes the famihes Phoenicopteridce, Megapodidce^ Cracidce, Turnicidce, Podicipedidce, and 
family groups of the Ratitce, from among one another. It is apparently only a generic charac- 
ter in Psittad, and in Cypselidcs, ArdeidcB and Alcidce. 
Reaching the skull, the carotids burrow in the bone, between the basitemporal plate and 
the true floor of the skull, and enter the cranial cavity by the " sella tui'cica" (the original 
pituitary space) ; their anastomosis furnishes a sort of circle of Willis." (Figs. 66, 69, 70, ic) 
