204 



GENERAL ORNITHOLOGY. 



and are termed aves leevo-earotidince (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 

 pneuinogastric nerve; such birds are aves hicarotidinae ahnormales (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 conjundo-carotidinai. 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 



Figs. 90-95. — Diagrams of carotid arteries of birds : 7i, root of aorta ; a, arch of aorta, to tlie right side ; li, left 

 innominate ; ri, right innominate ; Is, left subclavian ; rs, rigbt subclavian; Ic, left carotid; re, right carotid (1) 

 Fig 90. Aves bicarotidinte normales, with two carotids, both alike. (2) Fig. 91. Aves /(Evo-carotUlhifr, with left 

 carotid only. (3) Fig. 92. Aves bicarotUUnce nbnormales, certain parrots, with two carotiils. not alike. (4, 5, 6) 

 Aves conjuncto-carotidina:, 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 Sbufeldt 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 CypselideB ; in TrogonidcB, 3Ieropida;, 

 Upujndce, Rhamphastida, some Psittad, the Turnicidce, Megapodida, Podicipedido', Alcida:, 

 Rheidee, ApterygidcE. Thus in Passeres, Columha;, Accipitres, GraJlce, 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 families Phanicopterida, Megapodida, Cracidce, Turnicido', Podicipedidce, and 

 family groups of the Ratitte, from among one another. It is apparently only a generic charac- 

 ter in Psittad, and in Cijpselidce, Ardeidce and Alcida. 



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 tuj-cica " (the original 

 pituitary space) ; their anastomosis furnishes a sort of " circle of WiUis." (Figs. 66, 69, 70, ic.) 



I 



