ON THE ANATOMY OF THE NORTHERN BELUGA. 413 
of 12 inch, and measures 1 inch in diameter at its opening into the spiracle. 
They run obliquely forward and upward, their blind extremities lying between 
the integument and the wall of the skull, and contain a quantity of thick 
mucous-like material. Each is invested by a thick layer of muscular fibres, the 
exact arrangement of which could not be satisfactorily made out, owing to the 
separation of the soft parts from the cranium. 
The number of the nasal sacs in Beluga appears to differ from that of the 
other whales in which these have been accurately described. According to 
HuntTer,* there are two pairs in the porpoise, whilst in G'lobiocephalust and 
Lagenorhynchus{t Dr Muritz describes three pairs, to which in Grampus Rissoanus§ 
a seventh must be added. The position of the nasal sacs in Beluga, projecting 
forward as they do from the anterior wall of the spiracle, and lying underneath 
the integument covering the maxillary bones, justifies us in regarding them as 
homologous with the premaxillary sacs described by Dr Munriz in the species 
above mentioned. It is, however, to be observed, that in respect of the 
diminutive size of these sacs, Beluga differs much from the other forms referred 
to. As already stated, the exact arrangement of the muscles surrounding 
these sacs could not be satisfactorily determined ; but this is the less to be 
regretted in view of the very elaborate description given of them by Dr Muriz 
in other cetacean forms. 
Larynx.—The Cartilages. 
Thyroid.—The alee of the thyroid cartilage join inferiorly at a somewhat 
obtuse angle, forming a broad cartilaginous plate, which measures 2 inches in 
its antero- posterior diameter. Each ala diminishes rapidly to a depth of 4 
an inch at its lateral aspect, and then as suddenly expands in a crescentic 
manner giving rise to the cornua of the thyroid cartilage. Of these the anterior 
(superior) measure 3th of an inch in length, and are curved downwards at their 
extremities, whilst the posterior (inferior), measuring 14 inch in length, are 
curved downwards and forwards; the latter articulate by their extremities 
with the postero-external surface of the cricoid cartilage close to the posterior 
margin of the latter. The anterior margin of the thyroid cartilage affords 
attachment to the thyro-hyoid ligament. 
The cricoid cartilage, as noted by Barciay and NEILL in their specimen, 
is deficient inferiorly, an interval of + of an inch separating its lateral halves. 
Superiorly the cartilage measures 2 inches in depth, and presents a well-marked 
median ridge ; the anterior border is vertical in its upper part, but beyond the 
facets for articulation with the arytenoid cartilages, it slopes rapidly backwards 
and downwards. The flat articular surface for the reception of the arytenoid 
* XVI. p. 335. UL pi245. t V. p. 146, & Xepy 125: 
MOb. <XiX, PART I. 5 O 
