1901.] XAETNX OP CERTAIN WHALES. 285 



to the thyroid cartilage, and whose lower end is seen projecting 

 through the muscles (PL XXV. fig. 1) ; the upper end is in this 

 young Eorqual very thin, and the margin is reflected to support the 

 overlying mucous membrane ; the ridge supporting the " cushion " 

 is of short extent and does not reach the upper end. 



It measures 3^ inches in length; | inch deep at its base, 

 which is I inch luide, while the upper region is | inch wide. 



Before passing to a consideration of the muscles connected with 

 the cartilages, reference may be made to the form of the laryugeal 

 cartilages in Balcena mysticetus, which are fully and beautifully 

 figured by Eschricht and B-einhardt (1866). 



The form of the cartilages is very similar in the Right Whale 

 to those of the Rorqual, though, as would be expected, the 

 proportions of the various cartilages are slightly, but not markedly, 

 different ; the only important divergences are that the posterior 

 processes of the right and left aiytenoids are united behind 

 the entrance to the larynx, and the smaller size of the 

 epiglottid cartilage, while the body of the thyroid is of very much 

 greater extent than in the Rorqual ; nevertheless these two 

 members of the Mystacocetes have a larynx formed on one plan, 

 and this plan is very different from that of the Odontocetes. 



The Musculature of the Larynx. 



Drs. Carte and Macahster gave a detailed account of the 

 various muscles of the larynx — both extrinsic and intrinsic — for 

 iJaZ(:eno^ji(era,andIhavemade no attempt here to go over this ground. 

 I shall content myself with referring to those only that are con- 

 spicuous in this whale, and those that are of interest in contrast 

 with the larynx of Cogia. Carte and Macalister recognize 17 

 muscles, intrinsic muscles, in the larynx ; most of these I have 

 identified. 



1. The crico-fJvyroid muscle (PI. XXV. fig. 1, C.t.) is of consider- 

 able size ; it arises from the hinder half of the latero-ventral face of 

 the cricoid (body) ; the muscle-fibres pass forwards and outwards, 

 diverging as they go, to be inserted on the inner surface of the 

 posterior cornu of the thyroid. 



2. The ventral surface of the larynx is occupied by a great 

 bundle of muscle, longitudinally disposed in the middle line ; 

 on dissection it is found that this mass of muscle forms part of 

 the wall of the sublaryugeal pouch, and can readily be separated 

 into an external layer of longitudiual muscles and an inner sheet 

 of circular fibres. Carte and Macalister describe and figure only 

 the latter, and state that " the thick walls are almost entirely 

 composed of circular fibres." 



(a) The longitudinal muscles of this sublaryugeal sac take their 



origin in the body of the thyroid, to which they are attached 



^in the sides of the V-shaped notch (PI. XXV. fig. 1, T.c.) and on 



the inner face in the mid-line. From their point of origin the 



fibres spread out on both sides, forming two more or less distinctly 



