412 DR MORRISON WATSON AND MR ALFRED H. YOUNG 
the stylo-hyal element, and is inserted into the margin of the palate correspond- 
ing to the junction of the latter with the tongue. 
Inter-hyoideus Muscle arises from the whole length of the anterior border of 
the thyro-hyal, as well as from the outer border of the basi-hyal bone. _ Its fibres 
pass horizontally forward to be inserted into the stylo-hyal bone from end to 
end, as well as into the outer border of the cerato-hyal cartilage. This muscle 
fills wp the interval between the various parts of the hyoid bone, and is concealed 
by the hyo-glossus. 
The muscle does not differ much from that described by Murre* in Globio- 
cephalus, by Stanniust in the porpoise, or by CARTE and MACALISTER{ in 
Balenoptera. The latter authors describe it as divisible into three portions, 
which they name the superficial hyo-ceratic, the deep hyo-ceratic, and the 
kerato-pharyngeus. 
LARYNGEAL AND RESPIRATORY ORGANS. 
Blow Hole.—The blow hole, situated on the top of the head 114 inches 
behind the anterior extremity of the upper jaw, and 2 inches posterior to the 
level of the eye, is crescentic in form, with the concavity directed forward, and 
is considerably narrower than the chamber into which it leads. Its posterior 
lip overlaps the anterior. The thick cuticle of the exterior of the animal 
passes just within these lips, where it gives place to the mucous membrane of 
the nasal chamber. The latter is of a pure white colour, and on the anterior 
wall of the spiracle is raised so as to form two well-marked longitudinal bands, 
extending from the lower or laryngeal aperture obliquely upward and outward 
toward the external orifice of the spiracular cavity. From each of these bands 
others pass more or less horizontally outward, and subside on the lateral walls 
of the chamber. On the spaces between these bands are numerous small 
apertures indicating the ducts of mucous glands. Some of these, of large 
size, are formed by the junction of several smaller ducts, whilst others, and 
these form the majority, correspond to the ducts of isolated glandules. The 
apertures with their associated glands are found in abundance on the anterior 
and lateral walls of the spiracle, but much more sparingly on its posterior wall, 
where they are confined to its lower part. So far as the form and position of 
the blow hole is concerned, Beluga agrees closely with Grampus, G'lobiocephalus, 
and Lagenorhynchus. 
Nasal Sacs—Situated on the anterior wall of the spiracular cavity are the 
openings of the nasal sacs, which are two in number, one on either side of the 
middle line. The upper margin of that of the right side is 3th of an inch, and 
that of the left 14 inches from the margin of the blow hole. Each has a depth 
* II p, 264, Seay fa, t I. p. 235. 
