mong the
_Carnivora, Hyaenictis_ and _Ictitherium_ as intercalary, or, perhaps,
linear types between the _Viverridae_ and the _Hyaenidae_.

Hardly any order of the higher _Mammalia_ stands so apparently
separate and isolated from the rest as that of the _Cetacea_; though
a careful consideration of the structure of the pinnipede _Carnivora_,
or Seals, shows, in them, many an approximation towards the still more
completely marine mammals. The extinct _Zeuglodon_, however, presents
us with an intercalary form between the type of the Seals and that of
the Whales. The skull of this great Eocene sea-monster, in fact, shows
by the narrow and prolonged interorbital region; the extensive union
of the parietal bones in a sagittal suture; the well-developed nasal
bones; the distinct and large incisors implanted in premaxillary
bones, which take a full share in bounding the fore part of the gape;
the two-fanged molar teeth with triangular and serrated crowns,
not exceeding five on each side in each jaw; and the existence of a
deciduous dentition--its close relation with the Seals. While, on
the other hand, the produced rostral form of the snout, the
long symphysis, and the low coronary process of the mandible are
approximations to the cetacean form of those parts.

The scapula resembles that of the cetacean _Hyperoodon_, but the
supra-spinous fossa is larger and more seal-like; as is the humerus,
which differs from that of the _Cetacea_ in presenting true articular
surfaces for the free jointing of the bones of the fore-arm. In the
apparently complete absence of hinder limbs, and in the characters of
the vertebral column, the _Zeuglodon_ lies on the cetacean side of the
boundary line; so that, upon the whole, the Zeuglodonts, transitional
as they are, are conveniently retained in the cetacean order. And the
publication, in 1864, of M. Van Beneden's memoir on the Miocene and
Pliocene _Squalodon_, furnished much better means than anatomists
previously possessed of fitting in another link of the chain which
connects the existing _Cetacea_ with _Zeuglodon_. The teeth are much
more numerous, although the molars exhibit the zeuglodont double fang;
the nasal bones are very short, and the upper surface of the rostrum
presents the groove, filled up during life by the prolongation of the
ethmoidal cartilage, which is so characteristic of the majority of the
_Cetacea_.

It appears to me that, just as among the existing _Carnivora_,
the wa