1901.] LARYNX OF CERTAIN AVHALES. 293 



but also to the outer surface. Only a short piece of the muscle 

 remained in connection with the larynx, but the anterior direction 

 of the fibres and tlie position of its attachment render it pi-obable 

 that it is the muscle of this name. 



2. Just below this is the sterno-thyroid muscle (S.t.), the fibres of 

 which pass obliquely backwards and downwards towards the 

 position occupied by the sternum. 



3. Separated from this muscle by a sheet of fibrous tissue is a 

 third large muscle (.r) whose identification is uncertain. The 

 fibres are directed antero-ventrally, i. e. downwards and somewhat 

 forwards, though the inclination is but slight, and they pass nearly 

 directly ventralwards. This mass of muscle is attached over 

 nearly the whole of the lower half of the thyroid plate between 

 the '• bay " and the ventral margin, which, however, it does not 

 reach. As the larynx had been cut away from the neighbouring 

 organs, and indeed cut across near the lower end, I am unable to 

 identify the muscle : perhaps it is an accessory sterno-thyroid. 



4. The dorsal edge of the posterior cornua and of the thyroid 

 plates also serves for the attachment of muscles, probably the 

 stylo-pharyngeal and the basio-thyro-hyoid (cf. Macalister, 1867). 



5. Grico-ihyroid muscle. — This is very small in Cogia and invisible 

 from without, as it is entirely concealed, partly by the posterior 

 cornu and partly by a fan-shaped tendon that passes from its 

 ventral edge across the " bay " to the thyroid plate. But when 

 this tendon is removed, a small muscle is exhibited (PI. XXV. fig. 4, 

 PL XXVI. fig. 6 a, C.t.). In its diminutive size it contrasts very 

 notably with the homologous muscle in Balcenoptera, and indicates 

 a very feeble mobility of the thyroid cartilage upon the cricoid- 



In some Odontocetes, e. g. Globicephcdus melas, according 

 to Murie (1867), this muscle is of " considerable size," while 

 Macalister mentions that in G. svineval the crico- thyroid is 

 attached " to the posterior edge of the thyroid cartilage," and 

 makes no mention of its attachment to the cornu. 



5. The crico-arytenoid muscle is here represented by a posterior 

 and lateral division (the latter being absent in Mystacocetes). 



The posterior muscle (PL XXV. fig. 5, Car.) is a large quadrate 

 mass arising from the dorsal face of the cricoid and passing for- 

 wards to the arytenoid, to the "processus muscularis" to which it is 

 attached. The lateral division (PL XXVII. fig. 18) arises from the 

 side of the cricoid, ventral of the thyroid facet, and some of its 

 fibres arise from the horn of the thyroid (as Murie states is also 

 the case in Glohiocephalus), and indicating the close relation of this 

 muscle to the thyro-arytenoid. 



6. The transverse arytenoid muscle is a thin sheet having the 

 usual relations, and forming the dorsal wall of the " aryteno- 

 epiglottidean tube." 



7. The aryteno-epiglottid muscle (PL XXVII. fig. 18, A.ep.) is 

 comparatively small, and connects the lower regions only of the 

 two cartilages. ■ 



8. Above this is a mtich stouter muscle, the thyro-epiglottid(T.ep.),. 

 which arises from the inner surface of the thyroid near its ventral 



Pfioo. ZooL. Soc— 1901, Vol. I. No. XX. 20 



