th completely developed
acromion and coracoid processes. The whalebone is long, slender,
elastic and white. The species which inhabits the South American,
Australian and New Zealand seas is the smallest of the
whalebone-whales, being not more than 20 ft. in length.

In contrast to the preceding is the great grey whale (_Rachianectes
glaucus_) of the North Pacific, which combines the relatively small
head, elongated shape, and narrow flippers of the fin-whales, with the
smooth throat and absence of a back-fin distinctive of the
right-whales. The whalebone is shorter and coarser than in any other
species. In the skeleton the cervical vertebrae are free, and the
first two ribs on each side expanded and united to form a large bony
shield. In the humpback-whale (_Megaptera longimana_ or _boops_) the
head is of moderate size, the whalebone-plates are short and wide, and
the cervical vertebrae free. The skin of the throat is fluted so as to
form an expansible pouch; there is a low back-fin; and the flippers,
which have four digits each, are extremely long, equalling about
one-fourth the total length of the animal. The acromion and coracoid
processes of the scapula are rudimentary. See HUMPBACK-WHALE.

The right-whales are built for cruising slowly about in search of the
shoals of small floating invertebrates which form their food, and are
consequently broad in beam, with a float-shaped body and immovable
neck. The humpback is of somewhat similar build, but with a smaller
head, and probably attains considerable speed owing to the length of
its flippers. The finners, or rorquals (_Balaenoptera_), which prey
largely on fish, are built entirely for speed, and are the ocean
greyhounds of the group. Their bodies are consequently long and
attenuated, and their necks are partially mobile; while they are
furnished with capacious pouches for storing their food. They chiefly
differ from the humpback by the smaller head, long and slender build,
small, narrow, and pointed flippers, each containing four digits, and
the large acromion and coracoid processes to the low and broad
scapula. Rorquals are found in almost every sea. Among them are the
most gigantic of all animals, _B. sibbaldi_, which attains the length
of 80 ft., and the small _B. rostrata_, which does not exceed 30.
There are certainly four distinct modifications of this genus,
represented by the two just me