Dorsal fin high, erect, compressed, falcate, about three-fourths the entire length from the nose. Pectoral fin moderate, with four short fingers of four or six phalanges. Vertebræ 55 or 64. Cervical vertebræ not anchylosed. Neural canal oblong, transverse. * _Vertebræ 60 or 64; first rib single-headed_ (cf. p. 54). 1. BENEDENIA. Benedenia, _Gray_, _l. c._ pp. 114, 135; _Synops. Whales & Dolph._ p. 2. Rostrum of skull narrow, attenuated, with straight slanting edges. Second cervical vertebra with two short truncated lateral processes. The first rib single-headed. 1. Benedenia Knoxii. B.M. Benedenia Knoxii, _Gray_, _l. c._ pp. 138, figs. 24-26; _Synops. Whales & Dolph._ p. 2. Benedenia boops, _Gray_, _Synops. Whales & Dolph._ tab. 32. f. 1, 2 (cervical vertebræ). Inhab. North Sea, coast of Wales. 2. PHYSALUS. Physalus, _Gray_, _l. c._ pp. 114, 139; _Synops. Whales & Dolph._ p. 2; _Lilljeborg_, _N. Acta Upsal._ 1867, p. 72. Rostrum of the skull narrow, attenuated, with straight sloping sides. Second cervical vertebra with a broad lateral process, with a large perforation at the base. First rib single-headed. Sternum trifoliate, with a long slender hind process. Fingers shorter than the forearm-bones. Scapula very broad; acromion and coracoid process well developed. † _Lateral rings of the second cervical vertebra as long as the diameter of the body of the vertebra._—Gray, _l. c._ p. 374; Synops. Whales & Dolph. p. 2. 1. Physalus antiquorum. B.M. Ribs 14·14. Physalus antiquorum, _Gray_, _l. c._ pp. 144 (figs. 29-32), 374; _Synops. Whales & Dolph._ p. 2, t. 1. f. 6 (baleen), t. 32. f. 5, 6 (cervical vertebræ); _Flower_, _P. Z. S._ 1869, p. 604, pl. 47 (male). Balænoptera musculus, _Van Beneden_, _Ostéogr. Cét._ t. 12 & t. 13. figs. 11-24. Inhab. North Sea, Greenland, Hampshire, &c. 2. Physalus Duguidii. Ribs 15·15. Physalus Duguidii, _Gray_, _l. c._ p. 158, figs. 33-35; _Synops. Whales & Dolph._ p. 2. Inhab. North Sea, Orkneys. †† _The lateral rings of the cervical vertebræ shorter than the diameter of the bodies of the vertebræ._—Gray, _l. c._ p. 374; Synops. Whales & Dolph. p. 2. 3. Physalus patachonicus. Physalus patachonicus, _Gray_, _l. c._ p. 374, figs. 76-86; _Synops. Whales & Dolph._ p. 2. Inhab. River Plata. 4. Physalus brasiliensis. B.M. Physalus brasiliensis, _Gray_, _l. c._ p. 162. Balænoptera brasiliensis, _Gray_, _Zool. Ereb. & Ter._ p. 5. Inhab. Bahia. “_Mystica_ differs from the _norwega_ in having the back black and the belly and throat furrowed. Sometimes there are white spots on the side.