CETACEA. 58 
malia, though they do not present so many different forms. At 
the same time, it is true, that compilers like Lesson, who appear 
| n ot to have examined a single skull, have made many genera, 
- founded on very slight characters, and bring together species that 
“have very little relation to each other. 
_ For the purpose of more distinctly defining the species, it has 
n found necessary to divide them into several groups, so as to 
arrange them into what appears to be a more natural series, and 
_ eireumscribe the genera. 
: 
a 
14 
73 SYNOPSIS OF THE SUBFAMILIES AND GENERA. 
Y 
Ri ; : : 
_ A. Jaws tapering, the symphysis of the lower jaw short, not 
if half the length of the jaw. Dorsal fin generally distinct. 
% Pectoral fin ovate acute. Marine. 
a. Upper jaw toothless, lower jaw with only one or two teeth 
(which are often hidden in the gums) on each side. Beak 
of the skull keeled on each side, the keel being sometimes 
large, and forming a kind of reflexed wing on each side. 
Head with a short beak. yperoodontina. 
——— 
ae ar 
ae 
ma 
* 
eee ieee 
1. Hyperoopon. The beak of the upper jaw with a large 
erect wing-like expansion in front of the blowers ; lower jaw 
with two rudimentary teeth in front. 
anced’ 
v3 
2. Zipurus. Beak of upper jaw keeled on each side; lower jaw 
broad, bent down in front, with large compressed teeth in 
the middle of each side. 
3. De.puinoruyNcuus. Beak of upper jaw keeled on each 
side ; lower jaw nearly straight, with two or three small, rudi- 
mentary, conical teeth im the middle of each side. 
iii 
eg 
press 
is 
r 
5. Upper and lower jaw with few or deciduous teeth. Wings 
ea of the maxillary bones expanded and shelving downwards. 
£ ~ The beak short, deflexed. Forehead convex. Head round- 
ys ed, without any beak. Monoceratina. ; 
* : 
| i * Lower jaw toothless. 
# 
4. Monopon. Upper jaw of males with one or two very long, 
projecting, spirally twisted tusks. Dorsal none. 
ae 
a 
** Upper and lower jaw with conical, early deciduous teeth. 
5. Betuca. Dorsal fin none. 
= 
SRA: oe ane oe 
~ 
