REPORT ON THE ANATOMY OF THE PETRELS. 57 
The lateral position of the nostrils.‘ The presence of a distinet gluteus quintus 
muscle. The formation of the biceps hwmeri muscle, which gives off a patagial slip 
from its coracoidal head. The characteristic sternum. The absence of haemapophyses 
on the dorsal vertebra. The pneumatic os humeri. The generally pneumatic condition 
of the skeleton. The proportion of the manus to the humerus and ulna. 
The tongue and palate are also more or Jess peculiar, and in all the genera there are 
uncinate bones, no basipterygoid facets, and two large distinct accessory wing-ossicles ; 
the right liver-lobe is also distinctly the larger of the two. 
There are apparently three good genera of Albatrosses which may be distinguished, 
independently of external characters, as follows :— 
Diomedea. Tongue very short; uncinate bones more or less styliform. (Diomedea 
exulans and brachyura.) 
Thalassiarche. Tongue intermediate; uncinate bones styliform. (Zhalassiarche 
culminata.) 
Phebetria. Tongue much longer; uncinate bones flattened ; hallux better developed 
than in the other genera, and with an external claw. (Phaebetria fuliginosa.) 
Neglecting for the present the peculiar diving Pelecanoides, the remainder of the 
Procellariidee forms a natural group distinguished by the following characters from the 
Albatrosses (Diomedeinze) :— 
The more or less dorsal position of the nostrils, the form of which however varies, as 
has already been described, though they are never lateral. The absence of a gluteus 
quintus. The peculiar form of the biceps brachii muscle, which is in two separate 
_ parts, the humeral head forming a patagial slip. The presence of hemapophyses on the 
dorsal vertebrae, the centre of which are marked by more or less developed pneumatic 
depressions. The non-pneumatic humerus. The different pterylosis, and the nearly 
equal size of the lobes of the liver. The greater size of the hallux, which always has a 
distinct nail externally. (Quite absent in Pelecanoicdes.) 
Pelecanoides is, in some respects, as much specialised as the Albatrosses, though many 
of its modifications are distinctly traceable to its diving habits, as, e.g., the compressed form 
of the wing bones, the great development of the hypapophyses of the dorsal vertebre, 
the elongated sternum and pectoral muscles, the peculiar ribs. But it stands alone 
(amongst the Procellariide) in the absence of the ambiens muscle ; the peculiar disposi- 
tion of the femoral vein ; the absence of a hallux ; and the single interclavicular air-cell. 
Moreover, as in Bulweria only of other Tubinares, its myological formula is A.X., there 
being no accessory head to the femoro-caudal muscle. 
1 This feature, in which the Albatrosses are apparently more primitive than are either the Oceanitide or the other 
Procellariidee, can hardly, if my views about the relationships of these groups to each other be correct, be considered to 
have been a character of the common Petrel-ancestor. It may be more probably explained as due to arrested develop- 
ment during embryonic life, as a study of the development of the nostrils of other Petrels would probably show that 
these are actually, at some time, lateral, and subsequently coalesce. 
(ZOOL. CHALL., EXP.—PART XI. —1882.) Ls 
