SEAL-EMBRYOS. 17 
would not have expected is that, in spite of the presence of a large liver, the right 
lung extends backwards to a greater distance than does the left, thus giving the right 
lung a greater antero-posterior, as well as a greater transverse diameter. A small 
lobus impar was present connected with the root of the right lung. 
In specimen No, 24 the actual measurements were— 
Greater antero-posterior length—right lung : ; 88°5 mm. 
Greater antero-posterior length—left lung. ; : 85°3 mm. 
CIRCULATORY SYSTEM. 
As in the case of the other systems, the anatomy of the circulatory system of the 
Pinnipedia has been so fully and carefully described by Dr. Murie (Joc. cit.) that there 
remains but little to add, and I shall content myself by referring merely to a few 
points which have either been omitted by that author, or which I wish to accentuate. 
The heart appears to be somewhat disproportionately broad, being mainly due 
to the breadth of the right ventricle. The heart in specimen No. 24 furnishes the 
following measurements :— 
Total maximum breadth ‘ ‘ ; 55 mm. 
Total maximum length F : . 50 mm. 
Right ventricle breadth ‘ : : 35 mm. 
Right ventricle length . ; ; 50 mm. 
Left ventricle breadth . . ; : 20 mm. 
Left ventricle length . 2 : : 35 mm. 
The apex is traversely blunted, with a distinct notch separating the apices of the 
two ventricles. There is nothing in the interior of the heart requiring special mention 
beyond the fact that there is a well-marked moderator band. 
From the arch of the aorta spring three arterial trunks, an innominate, a 
left carotid, and a left subclavian, as Murie has shown to be the case in the Otariide 
but not in the Trichechide. There is but a single renal artery to each multilobular 
kidney. With regard to the middle sacral artery, around the morphology of which 
so much discussion has centred, I failed to discover, even in quite young specimens, 
any evidence of a primitive double nature. So far as I was able to determine, this 
artery was distinctly a median continuation of the dorsal aorta arising at the point of 
bifureation, perhaps slightly from the dorsal aspect. In one fcetus (No. 24) the 
middle sacral took origin from the dorsal aspect of the right common iliac artery, just 
at its commencement; I could find no corresponding branch arising from the left 
common iliac. 
The middle sacral itself, as one would expect from the very reduced size of the 
tail, is an exceedingly slender vessel. About the distance of a couple of vertebree from 
the point of origin it gives off a pair of bilaterally symmetrical branches which have 
all the appearance of ordinary segmental arteries. 
VOL. VY. D 
