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Show 562 MR. R. LYDEKKER ON ZEUGLODONT [NOV. 1, II. UNDETERMINED CETACEAN. (? Platanistidee.) The second species in the collection is represented by an associated series of four cervical, and the first dorsal, a lumbar, and a caudal vertebra; one of the cervicals being represented in PI. X X X V I I . figs. 1,1 a, and a caudal in figs. 2, 2 a of the same. The vertebrae indicate a Whale of the approximate size of the existing Beluga, with the last four cervical vertebrae free and of moderate length, and the lumbars and caudals likewise of medium elongation. The form of both the cervical and caudal vertebrae shows that these specimens are not referable to Zeuglodon caucasicus. The cervical vertebrae are represented by their centra, with the roots of the transverse processes attached ; the figured example having a width of 3*1 inches, a height of 2*2 inches, and an inferior length of 1 inch. The lumbar has a length of 2*3 inches, and a width of 2*6 inches across the anterior face of the centrum. With regard to their affinity, it is clear, in the first place, that, as they belong neither to Monodon or Delphinapterus, they cannot be referred to any other existing genera of Delphinidee, in all of which the first two cervicals are united, and the remainder extremely short, and generally more or fewer of them anchylosed. Free cervicals occur in the existing Ealcenoptera, Megaptera, and Rhachianectes, and the extinct Cetotherium. The small size of the specimens renders it, however, somewhat improbable that they belong to the Baleenidee ; and to this it may be added that they differ in certain respects from those of Baleenoptera. Moreover, we have no definite evidence of the occurrence of Baleen Whales in the Lower Miocene, to which it is quite probable that the Caucasian strata may belong. The existing Platanistidee and the numerous fossil forms referred by Prof. Cope to that family all have free cervicals, and, from the resemblance of the present specimens to some of the Miocene American representatives of that group described by that writer, I am inclined to think that they should be referred to the same family. The resemblance appears to be closest with the series of vertebrae figured l as Ixacanthus, and I am by no means certain that the Caucasian specimens do not indicate a member of the same genus, of rather larger size than its typical representative. Still, however, I do not propose to make any definite determination, leaving the matter with the expression of m y opinion that the specimens probably belong to the Platanistidee. III. INIOPSIS CAUCASICA (n. g. et sp.). The third Caucasian Cetacean is indicated typically by the hinder portion of a cranium, and also by some fragments of jaws and several vertebrae probably referable to the same form. It is much inferior in size to the preceding, and was of rather smaller dimensions than the existing Inia : that is to say, its total length was some six feet. 1 Cope, Amer. Nat. 1890, p. 603, fig. 1. |
