ON CERTAIN MUSCLES OF BIRDS. 221 
oil-gland and a peculiar sternum. The ambiens does not seem to be 
always developed. The great pectoral is double. 
2. The Fulmaride, with formula AB. X, the ambiens muscle 
present, two short ceca, a tufted oil-gland, and a characteristic 
sternum. Bulweria is exceptional in having its formula A. X, and 
therefore quite different from that of the Storm-Petrels. The great 
pectoral is double. 
The order CicontroRMES may be divided into five cohorts of 
somewhat different importance :— 
1. The Pelargi, with formula A. X Y, an ambiens muscle, a tufted 
oil-gland, intestinal ceca, and a double great pectoral muscle. 
2. The Cathartide, with formula A. X Y, an ambiens muscle, no 
- ewca, a nude oil-gland, and a double great pectoral muscle. 
3. The Herodiones, with formula A. X Y or X Y, no ambiens muscle, 
a single cecum coli, and a tufted oil-gland. 
4. The Steganopodes, which do not form so natural a family, in my 
eyes, as in those of many; for their myological formula is not the 
same in all, being 
In Phaethon A. XY, 
In Sula and Phalacrocoraz A. X, 
In Fregata A, 
from which it may be inferred that Phaethon approaches the Ciconiidze 
and Fregata the Accipitres. They all possess the ambiens, ceca, a 
tufted oil-gland, and the four toes included in a web, which is but im- 
perfectly developed in some. Sula and Phalacrocoraz, with Plotus, 
form one family, Phaethon another, Fregata a third, and Pelecanus a 
fourth. 
5. The Accipitres proper include the Falconide and the true 
Vultures (between which there is not even any subfamily structural 
difference), together with the Strigide. Their formula is A; the 
ambiens is present (except in the Strigidz), as are ceca, a tuft to the 
oil-gland, and an aftershaft (except in Pandion). 
The order CHARADRIIFORMES, including all the Schizorhinal birds, 
is a large one, and may be divided into two cohorts—a. the Columbe, 
and £. the Limicole. They all, except Arctica alle, have two carotids. 
a. The Columbe, including the Pteroclide, have a formula AB. XY Page 123. 
(except in Lopholemus, in which it is apparently A.XY). The 
ambiens muscle is sometimes present, sometimes absent. The oil-gland, 
if present, is nude; ceca may or may not be present; and the ptery- 
losis is a very diffused one. 
8. The Limicole have a tufted oil-gland and ceca; they form four 
families at least :— 
1. The Charadriide, with formula AB. XY and A. XY, and an 
ambiens muscle. 
