y descended
from the latter type, _Berardius_ being traced into the Miocene
_Mioziphius_, _Anoplonassa_ and _Palaeoziphius_, the last of which
shows signs in its dentition of approximating to the complicated
tooth-structure of the squalodonts.

Another line of descent from the latter, apparently culminating in the
modern _Platanistidae_, is represented by the family
_Eurhinodelphidae_, typified by the European Miocene
_Eurhinodelphis_, but also including the contemporary Patagonian
_Argyrocetus_ and the nearly allied European _Cyrtodelphis_. All these
were very long-beaked dolphins; and in _Argyrocetus_, at all events,
the occipital condyles, instead of being closely pressed to the skull,
are as prominent as in ordinary mammals, while the nasal bones,
instead of forming mere rudimentary nodules, were squared and roofed
over the hind part of the nasal chamber.

In the Miocene _Squalodon_, representing the family _Squalodontidae_,
the dentition is differentiated into incisors, canines and
cheek-teeth, the hinder ones of the latter series having double roots
and compressed crowns carrying serrations on the hinder edge;
generally the dental formula has been given as i. 3/3, c. 1/1, p. 4/4,
m. 7/7, the single-rooted cheek-teeth being regarded as premolars and
those with double roots as molars. Dr Abel is, however, of opinion
that the formula is better represented as i. 3/3, c. 1/1, p. (8 or
9)/9, m. 3/2; the teeth reckoned as molars corresponding to those of
the creodont Carnivora. The single-rooted cheek-teeth are regarded as
due, not to the division of double-rooted ones, but to the fusion of
the two roots of teeth of the latter type. In _Squalodon_ the nasal
bones were of the modern nodular type, but in the Miocene Patagonian
_Prosqualodon_ they partially covered the nasal chamber.

At present there is a gap between the most primitive squalodonts and
the Eocene zeuglodonts (_Zeuglodontidae_), which are regarded by
Messrs Max Weber, O. Abel and C.W. Andrews as the direct forerunners
of the modern-toothed whales, forming the suborder _Archaeoceti_. It
is, however, right to mention that some authorities refuse to admit
the relation of the Archaeoceti to the whales.

In the typical zeuglodonts the long and flat skull has large temporal
fossae, a strong sagittal crest, a long beak formed mainly by the
premaxillae (in place of the maxillae, as in mode