1870.] MR. J. B. PERRIN ON BALZNOPTERA ROSTRATA, 809 
cartilage as to afford a still further protective shield to it. ‘These 
muscles presented no difference from the very accurate description 
given of them by Carte and Macalister, except that the internal 
pterygoid was present, arising posterior and internal to the external 
pterygoid, and inserted anterior and internal to it, thus closely imi- 
tating the disposition of the corresponding muscle in the human 
subject. It was thin and small comparatively to the external ptery- 
goid. 
The Pelvic Bones.—These were two in number, both in a cartila- 
ginous condition, situated immediately above and on each side of the 
anal aperture, the inner extremity of the base of each being distant 
only an inch and three-quarters from it ; they were asymmetrical, the 
right being a quarter of an inch longer than the left, owing to its an- 
terior extremity being more pointed and prolonged a little more for- 
wards. Both presented two flattened surfaces, two borders (an in- 
ternal, concave, and an external, convex at its upper and concave at its 
lower part), and two extremities (an anterior pointed, and a posterior 
broad and directed obliquely from without downwards and inwards 
towards the anal aperture). At the summit of the outer convexity 
there was a small rough fibrous mass, about the size of a pea, in 
which were imbedded a number of very small cartilaginous plates. 
This is evidently the rudimentary representative of the femur, It 
is an easy matter to overlook this little mass, if attention is not par- 
ticularly directed to it. 
Both of these cartilaginous pelvic bones were enveloped in a dense 
fibrous capsule, which, stripped off, exhibited about the middle a 
prominent pinkish-red spot, studded over with minute puncta vas- 
culosa. In the left one only was there a decided centre of ossifica- 
tion. The right was entirely cartilaginous. 
Both of these rudimentary pelvic bones were imbedded in a mass 
of muscular tissue, so that care was required to detect them. 
The heart and great vessels, except that the former was more 
median in position and flattened, presented a similar disposition to 
those of the human subject. The weight of the heart was about 
100 oz. The walls of the left ventricle were an inch and a quarter 
thick, whilst those of the right ventricle were only about half an inch. 
In the right ventricle there was a very prominent fleshy column, 
situated on its inner wall, and about half an inch thick. It traversed 
the long axis of the ventricular cavity. From the middle of this 
column a second or transverse one arose, which crossed the middle of 
the cavity to the right wall, where it divided into a number of smaller 
columns, continuous with those on the posterior wall. The pulmo- 
nary artery was very large; its diameter measured 37 inches in the 
interior, readily admitting a circular disk of this size without any 
distention. Its walls, however, were very thin in comparison with 
those of the aorta. 
The pulmonary semilunar valves were large. The right one had 
a small nodule of Arantius, the rest being destitute of it. 
The aorta, at its origin from the left ventricle, was two inches in 
diameter. As it approached the part from which the innominate 
