254 DB. J. MITRIE ON THE OEGAJSTIZATION OF THE CAAING WHALE. 



plications. As the difterent plicae meet they give rise to unequal-sized trapezoidal 

 • elevations, many of which are perforated by glandular orifices, which doubtless secrete 

 abundantly during the process of deglutition. 



As Macalister has not failed to note, there are a pair of thick palato-glossi, whose 

 transverse fibres line the roof of the moutli, in my specimen having a breadth of more 

 than six laches. Some few of the anterior fibres continue to the fraenum liuguse ; others 

 posteriorly are lost among those of 'the palato-pharyngeus and constrictores. That the 

 above can act as a sphincter isthmi faucium, " capable of occluding perfectly the 

 aperture of the pharynx," I quite acquiesce in ; but this is aided to a remarkable extent 

 by the presence of a palato-pharyngeal muscle, likewise recorded by the above author', 

 and well developed in my specimen. 



By phar^-ngo-laryngeal valley, I mean the deep groove rimning roimd and within the 

 sphincter which grasps the glottis (vide fig. 13). The inner wall of this sulcus is formed 

 by a dipping inwards of folds of the postpharjiigeal region. Its depth is irregular, half 

 an inch at the sides, but shallowing m front and behind, where it is cranially attached. 



The elongated glottis is firmly grasped by the so-called sphiacter, the latter leaving 

 only an elliptical aperture, whose fleshy rim is about half an inch thick when cut 

 through. According as the outer walls are contracted or relaxed, so are the pair of 

 gutters or lateral chamiels of the floor of the pharynx narrowed or otherwise. The 

 lining membrane of this latter portion of the phar}'nx is smooth, or, at most, minutely 

 puckered. The postnarial passages possess great numbers of mucous glands. Some of 

 these project sUghtly ; others are embedded in shallow cavities, varying from the size of 

 a hemp-seed to twice that. Some are locular, and the whole give a punctated character 

 to the membrane, contrasting with the smoother superficies of the pharyngeal floor. 



The posterior narial passages, moreover, possess each a muscular layer, above chiefly 

 composed of longitudinal fibres. These, as they descend or proceed backwards, increase 

 in thickness, and the fleshy bundles assume an oblique and spiral direction, ultimately 

 becoming circular as they merge into what is usually entitled the superior pharjiigeal 

 constrictor. Some of the fibres of this can be traced downwards and backwards to the 

 surface and angle of the thyroid cartilage. Others, the enormously developed circular 

 ones, constitute chiefly the posterior wall of the pharynx, where they meet from the 

 opposite sides in strong, glistening tendinous fibres, covered by a narrowed portion of 

 of the inferior constrictor. The constrictor superior, besides, has attachments to the 

 posterior border of the palate and to the uiternal pterygoid plates. 



The constrictor medius is likewise very strong, broad, and fleshy ; attachments, side 

 and lower surface of the thyroid cartUage, and upper surface of the constrictores superioris 

 et inferioris. The last-mentioned muscle is considerably thinner than the others. Its 

 narrow upper point has been spoken of with the superior constrictor ; its other attach- 

 ments are the inner surface of the thyroid cartilage and descending process; the 

 posterior fibres mingle with the cuxular layer of the oesophagus. 



' See P. Z. S. 18(37, p. 480. 



