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Show 58 PROF. W. B. BENHAM ON THE OSTEOLOGY [Feb. 4, column, and that the last (13th) rib is imperfectly ossified and that the bone does not reach up to its vertebra, except possibly in very old individuals. The Sternum. As far as I have been able to discover, the sternum of this whale has not yet received an adequate description. It wTas only partially recovered by Wall, who gives but a short account of the imperfect bone, while it is not referred to either by von Haast (4) nor by Y a n Beneden & Gervais. In the Parakanui specimen the sternum (PI. III. fig. 4) consists of three sternebra?; the first and second formed of a single bone apiece, the last of a pair of small bones. Each sternebra is capped by cartilage at each end, and the posterior end is bifid. The anterior end of the sternum is bent slightly upwards, but otherwise the bones are flat; the thickness increases from the anterior end, where it is 8 mm., to the hinder end, which is 13 m m . in depth. The first two sternebra? have rounded lateral margins, while this margin, in the case of last pair of bones, is an abrupt slope downwards and outwards from the dorsal surface, with a sharp but obtuse upper and a sharper acute lower edge- the ventral surface of this last sternebra being wider than the dorsal surface. There are four cartilaginous sternal ribs, measuring 90, 75, 60, and 30 m m . respectively. The following measurements were made :- miliim. Total length, including cartilage 260 Greatest breadth 155 Least breadth 45 Length of the first bony sternebra1 along the lower surface 90 Greatest breadth 100 Breadth at posterior end 60 Thickness (dorso-ventrally) in middle 10 Length of second bony sternebra 76 Breadth at anterior end 54 „ in middle 43 ,, at posterior end 51 Thickness 12 Length of each ossicle of the 3rd sternebra 31 Greatest breadth 20 Thickness 13 The Hyoid. The hyoid is very briefly referred to by Wall, and rather more fully described (with a figure) by Y a n Beneden & Gervais. 1 Since the cartilages are only exceptionally preserved, the measurements of the bones are also given. |