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The common Dolphin is distinguished by a single blow-hole and numerous conical teeth.

Dolphin

The common Dolphin is distinguished by a single blow-hole and numerous conical teeth.

A small cetacean that is related to whales and dolphins.

The Porpoise

A small cetacean that is related to whales and dolphins.

"Whale is a name that may be taken as equivalent to Cetacean, and applied to any member of that order of mammals, which inculdes two great sets: the toothed whales, such as sperm whale and dolphin, and the whale-bone whales, such as right whale and rorqual, in which the teeth are only embryonic. The order Cetacea is usually divided into three sub-orders: (1) the Mystacoceti or Balænoidea, baleen or whalebone whales; (2) the Odontoceti or Delphinoidea, toothed whales; and (3) the Archæoceti or extinct Zeuglodonts. The differences between the extant sub-orders are so great that any idea of the close relationship must be abandoned; their common ancestry must be far back, and indeed it is doubtful whether our classification might not be brought nearer the truth by recognizing two distinct orders. Less specialized than the modern types are the extinct Zeuglododonts of the Eocene period, but it is by no means certain that they should be included within the order Cetacea."—(Charles Leonard-Stuart, 1911)

Whale

"Whale is a name that may be taken as equivalent to Cetacean, and applied to any member of that order…