296 



PEOF. W. B. BENHAM ON THE 



[Apr. 2, 



examination of the young of several species of Whales \ put for- 

 ward the view that part of this supra-arytenoicl is also equivalent 

 to the cartilage of Santorini. He, moreover, believes that the 

 condition of the cartilage in the Cetacea is a primitive one. 



Now, 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 PL XXVII. fig. 17), in 

 the manner in which the cartilage of Wrisberg sliould lie ; and 

 in my 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 



Diagrammatic longitudinal section through the larynx of A. Man ; B. Balce- 

 noftera ; C. Cogia. In each : — a, arytenoid ; b, cartilage of Santorini ; 

 c, cartilage of Wrisberg ; d, epiglottis ; e, tliyroid ; /, 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, ad- 

 mitting, 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. 



The 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 Man this process — sup- 

 porting 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 Eorqual it passes almost vertically downwards, 



^ It does not appear, from the abstract of his paper given in the 'Zool 

 Jahresbericht,* that Thompson examined any Mystacocete. 



