Cervical vertebræ free: the first with an inferior posterior process, bifid at the end; lateral processes very short: the second with a strong dorsal process. Dorsal vertebræ with very high dorsal processes. Scapula very high, with very long acromion and coracoid processes. The arm-bone short. Forearms thick and short, scarcely so long as the upper arm-bone. Metacarpal bones seven, imbedded in cartilage. The second and third fingers very long, with six phalanges; the first finger very short, of two phalanges; the fourth strong, short, about as long as the first two phalanges of the third finger, of four phalanges; the fifth finger very short, slender, of three phalanges. The breast-bone ovate, scutate, notched in front. 1. Inia Geoffroyii. Inia Geoffroyii, _Gray_, _l. c._ pp. 226, 393; _Synops. Whales & Dolph._ p. 4; _Flower_, _Trans. Zool. Soc._ vi. p. 87, t. 25, 26, 27 (skeleton). Delphinus amazonicus, _Spix_, _Reise in Brasil._ t. iii. pp. 1119 and 1113, fig. 34 (bad). Inia Geoffrensis, _D’Orbigny_, _in Ann. Mus. Paris_, vol. iii. p. 23; _Gervais_, _Ostéog. Cét._ t. xxxii. Inhab. Brazil, river Amazon. “The number of the teeth in the different specimens of _Inia_ examined shows a considerable range of variation, presuming that they all belong to one species. In the one now described there are R. 26, L. 26 / R. 25, L. 27 = 104. The larger specimen in the British Museum, from Ega, has 28-28/26-27 = 109, and also two minute rudimentary teeth in the gum behind the last in the left maxilla. In the smaller skull from the same place there are 29-26/28-27 = 110. In the skull in the Paris Museum, brought by D’Orbigny, there are, according to Gervais, 33-33/33-33 = 132; but in the type specimen in the same museum, taken from Lisbon, the number is given by De Bainville as 26-26/26-26 = 104. In the Berlin skull the teeth are 34-32/33-32 = 131. Von Martius, in his diagnosis of the species, gives 28-28/29-29 = 114.”—_Flower._ Family 10. DELPHINIDÆ. Delphinidæ, _Gray_, _l. c._ pp. 228, 393; _Synops. Whales & Dolph._ p. 4; _Flower_, _Trans. Zool. Soc._ vi. p. 113. Head beaked. Teeth in both jaws, conical or compressed, permanent, without any internal lobe, occupying nearly the whole length of the jaws. Back rounded, with a falcate dorsal fin; rarely absent. Skull with the maxilla expanded over the orbit, and more or less turned up on the edges.