22 Guide to Whales, Porpoises, and Dolphins. 
Toothed Whales. ae popes of De) ioe form 
1e suborder Gdontoceti, differ in many 
points from Whalebone- Whales. They never have whalebone, but 
always possess teeth throughout life, although these may be few in 
number and confined to the lower jaw, and even rudimentary in 
character. The blow-hole, or external respiratory aperture, is 
single (the two nostrils uniting before they reach the surface), and 
is usually in the form of a transverse, crescent-shaped, valvular 
aperture, situated on the top of the head. Great want of 
symmetry characterises the skull; and the two halves of the 
lower jaw have a longer or shorter bony union. Toothed Whales 
are not only more numerous in species than Whalebone-Whales, 
but present much greater diversity of form; all the smaller 
members of the order belong to this group, and only one species 
(the Sperm-Whale) rivals in size the larger Whalebone- Whales. 
Existing Toothed Whales are divisible into numerous generic 
groups, which may be arranged in the following five families :— 
I, PaysetEerip®, with Physeter and Kogia. 
I]. Zrenupm, with Hyperoddon, Ziphius, Mesoplodon, and 
Berardius. 
IIT. Puaranistipm, with Platanista. 
TV. Inuipa&, with Inia and Pontoporia. 
V. DELPHINIDH, with Monodon, Delphinapterus, Phocena, 
Cephalorhynchus, Orcella, Orca, Pseudorca, Globi- 
cephalus, Grampus, Feresia, Lagenorhynchus, Del- 
phinus, Tursiops, Prodelphinus, Steno, and Sotalia. 
The leading characteristics of these families and of the more 
important generic groups into which they are divided will be 
found in the sequel. 
The true Sperm-Whale (Physeter macrocephalus 
Sperm-Whale . 0” Pl @ NYS Ta 
GF fig. 8) is the largest of the Toothed Whales, and the 
typical representative of the family Physeteride, 
Cachalot. “i”. ; 
which includes the Lesser Cachalot and a number 
of extinct Cetaceans. In both the living species functional teeth 
are restricted to the lower jaw, but there are numerous extinct 
Physeteride in which both jaws are furnished with a full series of 
teeth. In the existing species nearly all the ribs are two-headed ; 
the rib-cartilages do not ossify; the petroso-tympanice bones are 
firmly united to the skull, which has large crests behind the 
