Form robust. Upper jaw moderately arched. Two to four furrows on throat. No dorsal fin. The color is black, or very dark slate, thickly marked about the snout, lips, chin and jaws with white flecks and small spots. On the sides, breast and belly are many roughly elliptical, irregular grayish markings and white circular spots which are apparently the scars left by barnacles. The amount of white varies greatly with individuals, but is seldom entirely absent. The pectoral fins and flukes are black on both surfaces, with scattered white spots and circles. Average size, 40 feet; maximum size, 49 feet. Skull with a broad strip of frontal exposed upon the vertex. Nasals very long and broad. Cervical vertebræ all free. Anterior ribs with tubercles, necks and heads. Vertebral formula: cervicals 7, dorsals 14, lumbars 12, caudals 23. Total, 56. Habitat: North Pacific Ocean only. SPERM WHALE, CACHALOT _Physeter macrocephalus_ (Linn.) Size large and form massive. Head blunt. A single S-shaped blowhole at the end of the snout. Forty to 50 teeth in lower jaw. No functional teeth in upper jaw. A prominent “hump” on the back. The color is slate gray, with some white about the lower jaw and snout, which is crossed in every direction by long white lines (scars). White or gray patches are usually found about the umbilicus. Greatest length, 70 feet. The bones of the skull are elevated to form a high crest above and behind the nares. The rostrum is very massive and wide, but gradually tapers to the apex, and is concave. Lower jaw very long and narrow. Atlas free, but all the other cervical vertebræ united into a solid mass. Vertebral formula: cervicals 7, dorsals 11, lumbars 8, caudals 24. Total, 50. Habitat: cosmopolitan, in warm currents. KILLER WHALE, ORCA, GRAMPUS, THRESHER _Orca orca_ (Linn.) Form robust. Head pointed. Heavy pointed conical teeth in both jaws. An extremely high dorsal fin. The color is black, with an elliptical white spot on each side of head. The throat and breast are white and there is a trident-shaped area of white on the belly and flanks. A white or grayish patch is usually present just behind the dorsal fin. The flukes above are black, and below white except for a black band on the posterior margins and tips. Greatest length, 30 feet. Rostrum about equal in length to the cranial part of the skull, broad and flattened above, rounded in front. Teeth usually twelve in each jaw. Vertebral formula: cervicals 7, dorsals 11–12, lumbars 10, caudals 53. Total, 51–52. Habitat: cosmopolitan. WHITE WHALE, BELUGA, MARSOUIN BLANC _Delphinapterus leucas_ (Pallas)