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Show 296 PROF. W. B. BENHAM ON THE [Apr. 2, examination of the young of several species of Whales l, put forward the view that part of this supra-arytenoid is also equivalent to the cartilage of Santorini. He, moreover, believes that the condition of the cartilage in the Cetacea is a primitive one. N o w , in the case of Balcenoptera-where the condition of the " aditus laryngis" is less modified than in Cogia-the tips of the " wing" of the arytenoid cartilage enter the arytenoid body, very much as does the cartilage of Santorini in normal mammals; but the convex border, it seems to me, can scarcely be said to be " in the aryteno-epiglottidean folds " (see PI. X X V I I . fig. 17), in the manner in which the cartilage of Wrisberg should lie; and in m y opinion the " supra-arytenoid " of the Mystacocete is not altogether and completely homologous with that of the Odontocete. Thus in Cogia a considerable part of the inner (or ventral) margin of the " supra-arytenoid " may, perhaps, be regarded as supporting the arytenoid fold, which is extremely reduced in length, though from the examination of the adult of this form it Text-fig. Diagrammatic longitudinal section through the larynx of A. M a n ; B. Balanoptera ; C. Cogia. In each:-a, arytenoid ; b. cartilage of Santorini; c cartilage of Wrisberg ; d, epiglottis ; e, thyroid ; /, cricoid ; g, trachea ; m, thyro-arytenoid muscle. Intended to illustrate the composite nature of the " arytenoid" in the Cetacea, and the disposition of the thryo-arytenoid muscle. would not readily appear that this is the case. However, admitting, as I am quite willing to do, the truth of Thompson's views for the Odontocete, there is still, I think, a possibility that there is no cartilage of Wrisberg in the Mystacocete. Tbe lower portion of the " arytenoid " includes the processus muscularis and the processus vocalis ; this region is the real " arytenoid." And the chief point of interest lies in the great development, in Balcenoptera, of the processus vocalis (text-fig. 75) and the change in its direction. For in M a n this process-supporting as it does the vocal cord and part of the thryo-arytenoid muscle-is horizontal, with respect to the longitudinal axis of the larynx, while in the Borqual it passes almost vertically downwards, 1 It does not appear, from the abstract of bis paper given in the 'Zool Jahresbericht/ that Thompson examined any Mystacocete. |