Rows of small teeth in Ziphioid whales

In Ziphioid Whales the toothrows as a rule have been subject to pronounced reduction, so that the number of teeth of fairly large size is restricted to one pair in the lower jaw. Even these often are concealed in the gum and then must be regarded as functionless, though especially in old males the tips of these teeth protrude above the gum and may be used for the capture of the prey. In many species, besides the larger teeth in the lower jaw, rows of smaller teeth have been found in both jaws, often completely hidden in the gum, sometimes with their tips protruding. In Tasmacetus shepherdi Oliver these smaller teeth are of fairly large size, they show signs of wear against their antagonists of the other jaw, indicating that here they are functional. The much smaller teeth occurring in rows in both jaws of other Ziphioid Whales generally are regarded as rudimentary, though in one species, Mesoplodon grayi Von Haast, they constantly form a so distinct regular row on each side of the upper jaw that they seem to perform a distinct function. Moreover, in this species the tips of the small teeth always protrude above the surface of the jaw, an additional indication of a definite function. The data concerning the position of the larger teeth in the lower jaw and their size and shape may be summarized as follows. Hyperoodon. At the tip of the lower jaw as a rule one pair, usually concealed in the gum, in older specimens sometimes with the tips projecting. In some specimens on one or on both sides a second tooth closely behind the first, the second tooth generally slightly smaller than the first. The teeth are conical, sharp pointed, oval in cross section. In a fairly large male the length of the teeth was 38 mm, the long (antero-posterior) diameter 19 mm, the short (transverse) diameter 12 mm1). In female specimens the