ON THE ANATOMY OF THE NORTHERN BELUGA. 417 
the point of the fore finger. This pouch is subdivided into a number of little 
saccules, which communicate freely with one another. It corresponds in posi- 
tion to the ventricles of the larynx in other mammalia, projecting outwards 
behind the cartilage of the epiglottis, and being invested externally by the 
fibres of the thyro-arytenoid muscles ; inferiorly it is concealed by the thyroid 
cartilage. The pouches of opposite sides are separated by a well-defined mesial 
fold of mucous membrane. The sacculated character of the mucous membrane 
just described is not confined to the larynx, but extends to the upper portion 
of the trachea. 
Probably none of the soft parts in the greater number of species of cetacea 
have been more completely examined, or so fully described and figured, as 
those constituting the laryngeal apparatus. Comparing these descriptions* 
and figures with those here given of the corresponding parts in Beluga, it is 
evident that, in respect of general form, the laryngeal cartilages of Beluga 
resemble closely those of the toothed whales taken collectively, whilst among 
these they appear to approximate in character more particularly to those of 
Monodon monoceros. MAyeEr* figures, however, in the latter species, a direct 
union superiorly of the arytenoid cartilages, which is not found in Beluga. 
In the toothed whales both the epiglottidean and arytenoid cartilages are 
prolonged to an almost equal extent (this condition being more especially 
noticeable in the females of different species); they are, moreover, united 
together by fibrous tissue throughout their whole length, and terminate 
superiorly in rounded and expanded apices, so that a free tubular larynx with 
a glottis bounded by thickened lips results. 
To these sectional characteristics Beluga entirely conforms, and in this 
respect differs very strikingly from the group of whalebone whales. The 
latter are distinguished by very characteristic laryngeal features, which, never- 
theless, are distinctly of the cetacean type. A free conical larynx exists, 
much shorter, however, than that of the toothed whales, and with corre- 
spondingly short: epiglottidean and arytenoid cartilages, which do not possess 
expanded apices, and which, moreover, are not united together in the whole 
of their extent. Such union as does exist is limited to the basal portions of 
the cartilages, whilst their upper parts remain free, and hence “ the respiratory 
canals appear undoubtedly to be less completely closed before than in the 
toothed whales.”+ 
Escuricut and Retnnarpr} are of opinion “ that the most essential peculiarity 
in the larynx of whalebone whales, as compared with that of the toothed whales, 
consists in its allowing the mucous membrane of the respiratory canals, by 
means of an opening on its ventral surface, to appear in the form of a sac with 
* XIX. Taf. Ixxxiv. fig. 104, + “Cetacea,” p. 102, Ray Soc., 1866. 2x p. LOl, 
VOL, XXIX. PART I. 5 P 
