246 CETACEA 
Suborder’ ARCHAOCETI. 
Family ZEUGLODONTIDA. 
This group is formed to include certain extinct Cetacean-like 
animals at present only known by more or less fragmentary por- 
tions of their skeleton and teeth, and whose position and affinities 
are, therefore, still subject to doubt.1 
In the anterior part of both jaws the teeth are simple, conical, 
or slightly compressed, and sharp pointed. The first three in the 
upper jaw are distinctly implanted in the premaxillary bone, and 
so may be reckoned as incisors. The tooth which succeeds, or the 
canine, is also simple and conical, but it does not exceed the others 
in size. This is followed by five teeth having two distinct roots 
and compressed pointed crowns, with denticulated cutting-edges. 
The dentition is therefore ¢ 3, ¢ 4, p and m & = 36, resembling that 
of some Seals.? General form of the skull elongated and much 
depressed. Brain-cavity very small, and the skull between it and 
the orbits elongated and narrow. Temporal fosse very large. A 
strong sagittal crest. Rostrum long and narrow, differing from 
that of other Cetaceans in the large extent to which the premaxille 
form the sides of the anterior extremity. Nasal bones elongated, 
flat, and narrow, the opening of the anterior nares being over the 
middle of the elongated compressed rostrum. All the cervical 
vertebree free. The characters of the dorsal vertebree and mode of 
articulation of the ribs appear to have resembled those of Platanista 
rather than Balena, Physeter, or Delphinus. Lumbar vertebrae 
with elongated bodies, low neural spines, and the transverse pro- 
cesses placed low down on the bodies. Characters of the limbs 
not known with certainty.? 
All the known fossil remains belonging to the animals of this 
group may be referred, provisionally at least, to the genus Zeuglodon, 
so named because the first section of a molar tooth examined was 
taken from the base of the crown, where it was beginning to divide 
into the two roots, and looked like two single teeth “linked or 
1 In a recent memoir Professor D’Arcy Thompson has brought forward some 
arguments to show that the Zeuglodonts have no direct affinities with the Cetacea, 
but have on the other hand the strongest possible relation with the Pinnipede 
Carnivora. ‘‘On the Systematic position of Zeuglodon,” Studies from the Museum 
of Zoology, Dundee, vol. i. No. 9, 1890. 
2 An appearance in one specimen has been described by C. G. Carus as in- 
dicating a vertical succession of the teeth, but the evidence upon which this rests 
is by no means satisfactory, and appears to admit of another explanation. 
* A mutilated humerus of Zeuglodon cctoides has given rise to many con- 
jectures, appearing to some anatomists to indicate seal-like freedom of motion 
at the elbow-joint, while to others its characters appear to be truly Cetacean. 
