522 
Proceedings of the Royal Society 
The caudals behind the first were all grooved on the ventral sur- 
face, and the groove in many instances possessed considerable depth. 
The spines of some of the lumbar and the more anterior caudals had 
sharp bony outgrowths projecting from the posterior border. 
Ribs . — There were fourteen pairs of ribs. The 1st was flattened, 
and measured in a straight line 25 \ inches on the left side and 25 
inches on the right * the breadth of the sternal end of the 1st left 
was 4f inches. The 2nd rib was 37f inches long on the left 
side and 33J inches on the right side. The ribs increased in 
length, as far back as the 6th rib, which measured 4 feet 3 inches 
t i 
in a straight line; from the 7th to the 14th they diminished 
in size, and the last rib was 2 feet 3 inches in length ; they 
were slender rod-like bones. All the left ribs were separate bones, 
but the right 1st rib was fused with the 2nd at the sternal end, 
where they formed a plate of bone 13 J inches broad. The breadth 
was partly due to a broadening of the sternal end of the 2nd rib, 
and partly to the formation of bone in the 1st intercostal space, for 
a distance of 6 inches from the sternal end, which was fused with 
the borders of both the 1st and 2nd ribs, and, together with them, 
. ■/ a 
formed the broad plate above referred to. On the 3rd and 4th 
ribs Well-marked capitular processes extended from the vertebral 
t 
articular surface towards the body of the vertebra. Budimentary 
capitular processes were present on the 2nd and 5th, but were 
absent on all the other ribs. 
In all the skeletons of B. borealis which have previously been 
described, the 1st rib had the peculiarity of possessing two heads. 
In the Leyden specimen the cleft which separated these heads from 
each other had a depth of 5 inches (Flower). From the figure 
given by Budolphi of this rib in the Berlin skeleton, it is probable 
that the cleft had a similar depth. In Lilljeborg’s Bergen skeleton 
the 1st pair are considerably wider than the others, with the upper 
end forked or “ biceps,” and the lower rather dilated and much 
wider than the upper. In the Brussels skeleton, as figured by Van 
Beneden, one of the first ribs has the same character, and in the 
Museum of the Boyal College of Surgeons of England are the first ribs 
of two individuals of this species, which are also bicipital. M. Fischer 
does not describe the skeleton of the Bayonne specimen, but notes 
that the spinal end of the 1 st rib is bicipital. M. V an Beneden had the 
