I. CLASSIFICATION OF THE CETACEA
In order to make clear the relations to each other of the whales and porpoises I have given below a classification and brief diagnosis of the principal groups. The currently accepted subfamilies of the Physeteridæ and Platinistidæ have been omitted for the purpose of simplifying the classification.
Order Cetacea. Whales and Porpoises.
A. Suborder Mystacoceti. Whalebone Whales.
I. Family Balænidæ. Right and Fin Whales.
a. Subfamily Balæninæ. Right Whales.
Head long—skull much arched—whalebone long and very fine—no grooves on ventral surface—no dorsal fin—greatest length, 65 feet.
b. Subfamily Balænopterinæ. Fin Whales.
Head short—skull slightly arched—whalebone short and coarse—grooves on ventral surface—a dorsal fin—greatest length, 87 feet.
II. Family Neobalænidæ. Pigmy Right Whale.
Head short—skull greatly arched—whalebone long, slender and white—no ventral grooves—a dorsal fin—ribs very broad and flat.
III. Family Rhachianectidæ. California Gray Whale.
Head short and moderately arched—whalebone short, coarse and widely spaced—2 to 4 grooves on the throat—no dorsal fin—greatest length, 48 feet.
B. Suborder Odontoceti. Toothed Whales.
I. Family Physeteridæ. Sperm Whales.
Head large and blunt—a single blowhole—40 to 50 teeth in the lower jaw—no functional teeth in upper jaw—a dorsal hump—greatest length, 70 feet.
II. Family Ziphiidæ. The Ziphioid Whales.
Head pointed—snout produced in form of a beak—a single crescent-shaped blowhole on top of head—one or two pairs of functional teeth in lower jaw—no teeth in upper jaw—greatest length, 30 feet.
III. Family Delphinidæ. Porpoises.
a. Subfamily Delphininæ.
Medium size—two or more neck vertebræ joined—single crescent-shaped blowhole on top of head—teeth in both jaws—usually a high dorsal fin—greatest length, 30 feet.
b. Subfamily Delphinapterinæ. White Whale and Narwhal.
Medium size-head small and neck vertebræ all separated—single crescent-shaped blowhole on top of head—no dorsal fin-flippers very broad—greatest length, 20 feet.
IV. Family Platinistidæ. Fresh Water Porpoises.
Small size—neck vertebræ all separate—single crescent-shaped blowhole on top of head—all inhabit fresh or brackish water—greatest length, 12 feet.