350 RORQUALS CHAP. 
symphysis of the jaws to the middle of the belly is, as in other 
species, marked by furrows, forty to fifty-eight im number. The 
hairy covering is reduced (in an adult female) to thirteen hairs 
on each side of the lower jaw; in a foetus there were also seven 
hairs on each side of the upper jaw, as well as rather more on 
the lower jaw—altogether, forty-eight. This Whale appears to 
feed chiefly upon small Crustacea, especially the Copepod, Calanus 
Jinmarehicus. The number of baleen plates is about 330 on each 
side of the jaw. This Whale sometimes swims singly, but usually 
in schools of even as many as fifty. 
Rudolphi’s Rorqual (4. borealis) seems to be a_ perfectly 
inoffensive beast; 1t is said to be able to stay under water for 
as long a time as twelve hours. 
A smaller species than the last is B. rostrata—at the outside 
33 feet in length. Here the hairy covering is reduced ' to “ two 
small hairs on the integument covering the apex of the lower 
maxilla.” The colour is greyish black above, the underside 
white. On the other hand, B. sibbaldii, the Blue Whale, is the 
giant of its race, reaching a length of 85 feet. Its colour is a 
dark bluish grey, with small whitish spots on the breast. The 
dorsal fin is small and low with straight margins. 
B. musculus, the Finner, is intermediate in size—not more 
than 70 feet. It seems doubtful whether the “ sulphur bottom,” 
B. australis, of Antarctica and B. patachonica differ specifically 
from this.” 
The genus Megaptera is very near Balaenoptera, but differs 
from it mainly in the following external and internal characters. 
The dorsal fin is not very prominent, and its place is taken by a 
lowish hump, whence, indeed, the common name of this Whale, 
“Humpback.” The pectoral fin is unusually long, and the 
creature uses 1t to beat itself, the surrounding water, and, more 
playfully, its mates. The general outline of this Cetacean is 
more clumsy than that of Lalaenoptera. The most important 
internal difference is in the form of the scapula, which has at 
most a shght acromion and coracoid process. These are rather 
more pronounced, according to Messrs. van Beneden and Gervais,” 
1 Perrin, ‘‘ Notes on the Anatomy of B. rostrata,” Proc. Zool. Soc. 1870, p. 805. 
2 von Haast, ‘‘ Notes on a Skeleton of Balaenoptera australis,” Proc. Zool. Soc. 
1883, p. 592. 
3 Ostéographie des Cétacés, Paris, 1880, p. 130. 
