ON THE ANATOMY OF THE NORTHERN BELUGA. 425 
auricle presents but two caval openings. Whether these were provided with 
valves or the reverse could not be ascertained, as the heart had unfortu- 
nately been damaged before coming into our possession. Instead of a single 
opening of the coronary sinus we distinguish two. They are placed close 
together in the usual position of that sinus, and are the orifices of two large 
veins, the trunks of which are situated in the right auriculo-ventricular and 
right ventricular grooves respectively. Neither of these openings presents the 
slightest trace of a Thebesian or coronary valve. It thus appears that in our 
specimen a coronary sinus, properly so called, does not exist ; but whether this is 
to be regarded as the normal arrangement of the cardiac veins in Beluga catodon, 
or merely as an individual peculiarity of exceptional character, can only be 
decided by more extended investigation. The cavity of the right ventricle 
presents no feature worthy of note, except the large size of the columne 
carneee and musculi papillares. The right auriculo-ventricular valve consists 
of three cusps, which are arranged in the usual manner. It presents no trace 
of the remarkable perforation observed by Murie* in Gilobiocephalus melas. 
In the left ventricle the papillary muscles and fleshy columns are of enormous 
size, the latter inter-crossing in all directions. The valves do not present any 
deviation from the arrangement usually found in the mammalian heart. 
The Aorta arches over the root of the left lung. In addition to the 
coronary arteries for the supply of the heart, the arch of the aorta 
furnishes two innominate trunks, these E 
being derived from its transverse portion. 
Each innominate artery measures 2 inches, 
and terminates by dividing into a common 
carotid for the supply of the head and 
neck, and a subclavian which is distributed 
to the flipper. The common carotid runs 
a short course of about half an inch, and 
then divides into two trunks of equal size, 
both of which run forward towards the 
head. Doubtless these represent the ex- 
ternal and internal carotids, Their exact ona - sersk |, 
a Beluga, —Semi-diagramatic view of the aortic arch and 
distribution could not be traced, owing to hi its branches, reduced. 
the state of the parts. This was also the case with several large branches 
which, springing from the subclavian, passed to the parts about the scapula. 
With reference to such points in the anatomy of the circulatory system as 
are noted in previously described Reluge, we find that the account given by 
Wyman,t of the heart and aorta with its branches, agrees in the main with 
* II. p. 266, + IIL p. 608. 
VOL. XXIX, PART I, oR 
