_Range of Carnivora in Time._--Carnivora have been found in all the Tertiary deposits, and comprise a number of extinct genera and even families. Several genera of Canidæ occur in the Upper Eocene of Europe; but the most remarkable fact is, that even in the Lower Eocene are found two well-marked forms, _Palæonyctis_, one of the Viverridæ, and _Arctocyon_, forming a distinct family type of very generalized characters, but unmistakably a carnivore. This last has been found at La Fère, in the north-east of France, in a deposit which, according to M. Gaudry, is the very lowest of the Lower Eocene formation in Europe. _Arctocyon_ is therefore one of the oldest, if not the very oldest, of the higher forms of mammal yet discovered. {207}_Order V.--CETACEA._ FAMILY 36.--BALÆNIDÆ. (6 Genera, 14 Species.) GENERAL DISTRIBUTION.--Temperate and Cold Seas of both Northern and Southern Hemispheres. This family comprises the whalebone or "right" whales, the best known species being the Greenland whale (_Balæna mysticetus_). Allied species are found in all parts of the southern seas, as far north as the Cape of Good Hope; while some of the northern species are found off the coast of Spain, and even enter the Mediterranean. As most of the species indicated are imperfectly known, and their classification by no means well settled, no useful purpose will be served by enumerating the genera or sub-genera. FAMILY 37.--BALÆNOPTERIDÆ. (9 Genera, 22 Species.) GENERAL DISTRIBUTION.--Cold and Temperate Seas of both Hemispheres. This family comprises the finner whales and rorquals, and are characterised by possessing a dorsal fin and having the baleen or whalebone less developed. They are abundant in all northern seas, less so in the southern hemisphere, but they seem occasionally to enter the tropical seas. The best known genera are _Megaptera_ (7 species); _Physalus_ (4 species); and _Balænoptera_ (2 species); all of which have species in the North Sea. FAMILY 38.--CATODONTIDÆ. (4 Genera, or Sub-Genera, 6 Species.) GENERAL DISTRIBUTION.--All the Tropical Oceans, extending north and south into Temperate waters. This family, comprising the cachalots or sperm whales, and black-fish, are separated from the true whales by having teeth in the lower jaw and no whalebone. They are pre-eminently a tropical, as distinguished from the two preceding which are {208}arctic and antarctic families. The spermaceti whale (_Catodon macrocephalus_) abounds in the Pacific Ocean and in the deep Moluccan Sea, and also in the Indian Ocean and the Mozambique Channel. In the Atlantic it is scarce, although it occasionally comes north as far as our shores. The genera of Catodontidæ as given by Dr. Gray are, _Catodon_ (2 species?), Warm Eastern Oceans; _Physeter_ (1 species), "the black fish," North Sea; _Cogia_ (2 species), South Temperate Oceans; _Euphysetes_ (1 species), Coast of Australia. FAMILY 39.--HYPEROODONTIDÆ. (9 Genera or Sub-Genera, 12 Species.)