Caperea, _Gray_, _l. c._ pp. 78, 101; _Synops. Whales & Dolph._ p. 2; _Lilljeborg_, _N. Acta Upsal._ vi. 1867. First rib ⸺? Baleen ⸺? Tympanic bones irregular, rhombic; aperture irregular, much contracted at the upper end; the wide part not half the length of the bone. “Cervical vertebræ all united. First rib single at the upper, and very broad at the lower end. Bladebone (acromion) rudimentary. Coracoid process none.”—_Lilljeborg._ Vertebræ 55; the seven cervical all soldered by their bodies, and the spinous processes of the first five united into a single crest, and of the two last into a separate crest; each has a distinct upper lateral process and, except the seventh, a distinct lateral process. Upper lateral process of the atlas narrow, square, reflexed, and bent upwards; lower one thick, enlarged, and rounded at the end (Ostéogr. Cét. t. 3. f. 4, 5). Scapula with only a slight ridge in the place of the acromion (Ostéogr. Cét. t. 3. f. 7). Carpus cartilaginous, with five small bones. Skull with a slender arched beak. Lower jaw subcylindrical, thick near the condyle, rather attenuated in front. The first rib is very narrow above, and gradually becomes very broad below and deeply notched on the lower edge, which embraces nearly the whole length of the sternum; upper end with a single head. Second rib equally large at the free end, and not notched. Phalanges 1, 4, 5, 4, 3. I believe that the “_bonnet_” of the Sandwich-Islands whalers is only the “_topknot_” of the old male whale of this genus, or of a nearly allied species. 1. Caperea antipodarum. B.M. Caperea antipodarum, _Gray_, _l. c._ p. 101, f. 9; _Synops. Whales & Dolph._ P. 2. Balæna australis, _Desm. Diction_. Balæna antipodarum, _Van Ben._ _Ostéogr. Cét._ p. 46, t. 3; _Gray_, _Dieffenbach_, t. 1. Inhab. New Zealand. Skeleton, Mus. Paris. The seven cervical vertebræ are completely soldered by their bodies; and the first five spinal apophyses form a continuous crest, and the two last form a separate crest (Ostéogr. Cét. t. 3. f. 4, 5). The petrous portion of the skull short, small. The bladebone longer than broad, with only a slight indication of a process on the front edge. Upper lateral process of the axis square, bent back; lower process rounded at the end and prominent. 6. MACLEAYIUS. Macleayius, _Gray_, _l. c._ pp. 103, 371; _Synops. Whales & Dolph._ p. 2. Cervical vertebræ united into a single mass; upper lateral process of the atlas very broad, compressed, occupying the greater part of the side, truncated at the end. Lower margin close on the lower lateral process. Lower lateral process elongate, compressed, rather swollen in the middle, truncated at the end and bent forward, the upper processes of the second and third cervical vertebræ forming a crest (Cat. Seals & Whales, p. 105, f. 10, 11, and p. 372, f. 74, 75). Baleen ⸺? 1. Macleayius australiensis.