OCR Text |
Show 1892.] AND OTHER CETACEAN REMAINS. 559 three distinct forms, one of which was a Zeuglodont, the second a more typical Cetacean of relatively small size, and the third a still smaller dolphin-like Cetacean. The Zeuglodont remains indicate a very small species. In regard to the probable age of the deposit, it may be observed that although Zeuglodonts occur in America in the Middle Eocene, and in England in the lower part of the Upper Eocene (Barton beds), in Malta they are found in the Miocene, where one of the forms is of very small size. Moreover, since, with the exception of Zeuylodon and Squalodon, together with the problematical Baleenoptera (?) juddi, Whales are unknown in the Eocene, while we have two distinct forms in addition to the Zeuglodon from these deposits, it might seem that the age of the latter is Miocene rather than Eocene. So far as it goes, the evidence of the Zeuglodon might be in favour of the same view, since such a small form as the one before us might well be one of the last waning representatives of its race. With these preliminary remarks, I proceed to the consideration of the specimens themselves. I. ZEUGLODON CAUCASICUS, sp. nov. The Zeuglodont remains comprise the hinder part of a left mandibular ramus containing four teeth (PI. X X X V I . fig. 1), another fragment of a jaw with five broken teeth, a left humerus (PI. X X X V I . fig. 2), and an imperfect caudal vertebra (PI. X X X V I . fig. 3). The Zeuglodont nature of the figured jaw is shown by the teeth, in which the serrations are as fully developed on the anterior as on the posterior border, thus differentiating the specimen from the Squalodonts. The jaw is relatively deeper than in the so-called Zeuglodon hydrarchusl of North America, but the chief peculiarity of the specimen is its small size, which at once distinguishes it from the American form. The humerus (PI. X X X V I . fig. 2) agrees in relative size with the jaw, its total length being only 4'4 inches, whereas the corresponding bone of Z. hydrarchus preserved in the Museum at Haarlem measures 8'6 inches 2. In character both specimens agree very closely, although the European example is distinguished by the greater development of the deltoid crest (d), the more oblique form of the head (h), and the less upward extension of the great tuberosity (t) ; the upward extension of this tuberosity in the Caucasian specimen is, however, at least partly due to the effect of crush. Both bones are distinguished by the large size of the head, the compressed form of the 1 Dames and Gaudry regard this form as the female of the larger Z. cetoides, but Cope (Amer. Nat. 1890, p. 602), who alludes to it as Z. brachyspondylus, considers that it may belong to a distinct genus-Boryodon. That genus is typically represented by the small Boryodon pygmceus, Leidy. 2 There is a cast of this bone in the British Museum. 38* |