1901.] LARYNX or CERTAIN WHALES. 287 



The circo-arytenoid is a powerful muscle arising from the greater 

 part of the dorsal and lateral face of the cricoid, the latei*al 

 portion being concealed below the crico-thyroid. The muscle 

 passes forwards to be inserted in the apes of the processus 

 muscularis of the arytenoid cartilage. 



The lateral portion is not separable from the posterior portion 

 (as Carte and Macalister and others have pointed out) ; there is no 

 distinct lateral crico-arytenoid, it is one huge mass of muscle. 



5. The inter-arytenoid muscle has the usual disposition, and, as 

 already reniarked, arises from the " wing " of the arytenoids. 



6. The th>/ro-ari/tenoid muscle (PI, XXVII. fig. 17, T.ai\) arises 

 from the inner face of the body of the thyroid near the middle 

 line — precisely as in the human subject — and is inserted into the 

 ventral or inner surface of the body of the arytenoid, and partially 

 to the upper part of the posterior process of the latter cartilage, 

 above and external to the aryteno-epigJottid muscle. 



7. The latter muscle (^.ep.)— which is much less streaked by 

 blood-vessels — passes from the outer face of the wing of the 

 arytenoid, and also from the posterior process of the same, to 

 the epiglottid cartilage, which is embedded in muscle, and here 

 the substance of the muscle is penetrated by fibres of the hyo- 

 epiglottid and thyro-epiglottid. 



This aryteno-epiglottid in reality consists of a supero-internal 

 sheet attached to the arytenoid wing, and an infero-external 

 sheet attached to the aiytenoid process. These sheets are not 

 well defined on their outer surface ; but when the mucous 

 membrane of the larynx is dissected away their demarcation is 

 readily seen. 



8. The hyo-epiglottid muscle (H.ep.), when it reaches the epiglottis, 

 appears as a single muscle inserted in the antero-ventral face of 

 the epiglottid cartilage ; the fibres mingle with those of the 

 previous muscles, some passing forwards, and some curve upwards 

 round the side of the epiglottis. 



As to the extrinsic muscles of the larynx, I will only refer to two, 

 the tJiyro-hyoid and the sterno-thyroid (PI. XXV, fig, 1, TJi.,S.t.). 



The thyro-hyoid arises from the anterior region of the ventral 

 surface of the thyroid cartilage, along nearly its whole Avidth ; it 

 is triangular in outline, as the fibres converge forwards to be 

 attached to the hyoid cartilage, near the middle line. This 

 muscle is represented and described by Carte and Macalister, but 

 the existence of the sterno-thyroid in Bcdcenoptera is explicitly 

 denied by them, though it appears to have been recognized by later 

 authors. Certainly there is a muscle of considerable size attached 

 to the ventral face of the thyroid near the lateral margin where 

 the " cornu " arises, where fibres pass backwards as a broad sheet an 

 inch and more across, which is directed downwards and backwards 

 towards the sternum. Unfortunately I had cut through this 

 muscle without noting carefully its relations, while tracing out the 

 blood-vessels ; but it is, I think, pretty evident, from the direction 

 of its fibres, that it goes to the sternum. 



