525 
of Edinburgh, Session 1881 - 82 . 
middle of the body was slightly concave from side to side, and 
slightly convex from before backwards. The posterior border of 
the body was convex, and projected backwards considerably behind 
a line drawn across between the posterior border of the two great 
cornua. In this character it differed very markedly from both B. 
sibbaldii and B. musculus. The great cornu was flattened on its 
upper and slightly convex on its under surface, with the anterior 
border a little more rounded than the posterior ; its antero-posterior 
diameter was almost uniform until near the tip. In B. sibbaldii , 
again, the great cornu swelled out so as to assume a remarkable 
fusiform shape, and to a less degree this is also seen in B. musculus , 
The stylo-hyals were flattened on both surfaces and 13 J inches long. 
The hyoid measured between the tips of the great cornua 21 inches. 
The following table gives, in feet and inches, the principal 
dimensions of the skull i — 
FT. 
From anterior border of foramen magnum over vertex to 
tip of beak, . . „ . . .8 
From nasal end of superior maxilla to tip of beak, . . 6 
From. anterior border of foramen magnum to nasal end of 
superior maxilla, . . , „ *2 
Breadth across posterior ends of superior maxillae, . . 0 
Greatest breadth of skull, . . . . .3 
Breadth of skull at base of beak, . „ . .2 
Breadth of skull at middle of beak, . . .1 
Breadth of skull between middle of orbital borders of 
frontals, . . . „ 4 .3 
Length of skull in a straight line (condylo-premaxillary), . 8 
Length of beak, . . „ „ „ ,5 
Length of superior maxilla, . * . .6 
Length of premaxilla, „ * . . . Q 
Greatest breadth of superior maxilla behind base of beak, . 3 
Greatest breadth between outer borders of both premaxillse, 0 
Greatest breadth of space between both premaxillse, . 0 
From foramen magnum to upper border of occiput, . 2 
IN. 
91 
9 
04 
8| 
lOf 
6 
KX 
o 2 
n 
9 
3 
64 
1 
10 
8 
0 
I have compared the tympanic bones with those of B. rostrata — 
the smallest — and B. sibbaldii — the largest — of the fin whales. 
Their dimensions expressed in inches were as follows : — 
Immature. Adolescent. Immature. Adolescent. 
B. rostrata. B. borealis. B. Sibbaldii. B. Sibbaldii. 
Length, 3 ’5 4 *8 47 5 '3 
Breadth, .1*8 2 '2 2 '5 2 '6 
In B. rostrata the breadth index was 51, in borealis 46. The 
