Beluga Kingii, _Gray_, _Cat. S. & W._ p. 309; _Synops. Whales &. Dolph._ p. 9, t. 7. Inhab. Australia. 2. MONODON. Monodon, _Gray_, _l. c._ pp. 231, 310; _Synops. Whales & Dolph._ p. 9. Monoceros, _Gray_, _Cat. S. & W._ p. 393. Lateral expansion over the orbit shelving down. Teeth in both jaws very early deciduous. Male with one, rarely two, very long, projecting, spiral tusks in the left side of the upper jaw. Cervical vertebræ:—first free, thin; second and third united by the spinal processes. Bladebone with large coracoid and acromion processes. Fingers short. Vertebræ 50:—C. 7. D. 11. L. 6. C. 26. “In the skeleton of two males in the Museum of the College of Surgeons, the bodies of the second and third cervical vertebræ are firmly united.”—_Flower._ 1. Monodon monoceros. B.M. Monodon monoceros, _Gray_, _l. c._ p. 311; _Synops. Whales & Dolph._ p. 9; _Gervais_, _Ostéogr. Cét._ t. 44. f. 6-9. Inhab. North Sea. Family 15. PONTOPORIADÆ. Head long-beaked. Beak slender, smooth. Nostrils on the nape, crescent-shaped. Teeth in both jaws permanent, conical, with a swollen ring round the base. Dorsal fin short, trigonal. Pectoral fin short, truncated. Fingers 5, nearly equal; the thumb very short, of one joint; the index finger the longest, the rest gradually shorter to the little finger. Bladebone broad, with two ridges. Skull long-beaked, the beak compressed. Lower jaws united together nearly to the base. Cartilages of ribs ossified. Vertebræ 42:—C. 7. D. 10. L. 7. C. 18. 1. PONTOPORIA. Pontoporia, _Gray_, _Cat. S. & W._ pp. 230, 231 & 393; _Synops. Whales & Dolph._ p. 5; _Flower_, _Trans. Zool. Soc._ vi. p. 87; _Burmeister_, _An. Mus. P. Buenos Ayres_, p. 389. Stenodelphis, _Gervais_, 1847. Beak of the skull high, compressed. Symphysis of the lower jaw very long. 1. Pontoporia Blainvillii. B.M. Pontoporia Blainvillii, _Gray_, _l. c._ p. 231; _Synops. Whales & Dolph._ p. 5, t. 29 (skull); _Flower_, _Trans. Zool. Soc._ vi. p. 106, t. 28 (skull); _Burmeister_, _An. Mus. P. Buenos Ayres_, i. p. 387, tab. 23 (animal), tab. 25 & 26 (skeleton). Inhab. South Atlantic, Monte Video. The animal figured by Gervais as _Delphinus (Stenodelphis) Blainvillii_ (Voy. Amér. Mérid. t. 23) differs from Burmeister’s figure in having an elongated subfalcate pectoral fin, and a higher dorsal, and a broad white streak, commencing from the blower and extending down the back to near the tail. If this is not a figure of the animal seen at sea, which I suspect it must be, it must be a different species. Suborder VI. ZIPHIOIDEA. Ziphiidæ, _Gray_, _Cat. S. & W._ p. 326. Ziphioidea, _Gray_, _Synops. Whales & Dolph._ p. 9.