770 
MAMMALIA, 
CONTRASTS BETWEEN THE TWO SUB-ORDERS OF 
LIVING CETACEANS 
MystTacocetTI or BALZNOIDEA, 
baleen Cetaceans. 
OponToceET! or DELPHINOIDEA, 
toothed Cetaceans. 
The teeth are absorbed before birth, 
Whalebone or baleen-plates develop as 
processes from the palate. 
The skull is symmetrical. 
The nasals roof the anterior nasal pas- 
sages, which are directed upwards 
and forwards. 
The maxilla does not overlap the orbital 
process of the frontal: 
The lachrymal is small, and distinct 
from the jugal. 
| The tympanic is ankylosed to the peri- 
otic. 
The rami of the mandible are arched out- 
wards, and have no true symphysis. 
All the ribs articulate only with the 
transverse processes of the vertebra, 
the capitulum being imperfect. 
The sternum is a single piece, and arti- 
culates with a single pair of ribs ; the 
sternal ribs are not ossified. 
The external nostrils are separate. 
The olfactory organ is distinctly de- 
veloped. 
There is a short cecum. 
Examples.— 
The right-whale (Balena), the 
hump-back (Megaptera), the 
rorqual (Batenopiera). 
The teeth persist after birth, and are 
generally numerous and functional. 
There is no baleen. 
The skull on its upper surface is more 
or less asymmetrical. 
The nasals, always small, do not roof 
the anterior nasal passages, which are 
directed upwards and backwards. 
The maxilla covers most of the orbital 
process of the frontal. 
The lachrymal is fused to the jugal, or 
is large, and helps to roof the orbit. 
The tympanic is not ankylosed to the 
periotic. 
The rami of the mandible are straight, 
and form a symphysis. 
Several anterior 2-headed ribs articulate 
by capitula with the centra. 
The sternum has usually several seg- 
ments, with which several usually 
ossified sternal ribs articulate. 
The nostrils unite in a single blow-hole 
on the top of the head. 
The olfactory organ is rudimentary or 
absent. 
There is no cacum, except in Plata- 
nista. 
Examples.— 
The sperm-whale (Physeter), the 
dolphin (Delphinus), the por- 
poise (Phocena), the ‘ Gram- 
pus” (Orca), the Ca’ing-whale 
(Globicephalus), Grampus, the 
narwhal (Monodon), with an 
enormous tusk in the male. 
