352 MR. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-WHALE. 
The first rib (Pl. LX. fig. 2) is very different from the others in form. Though 
by far the shortest, it weighs absolutely more than any of the others, this being 
occasioned by its great thickness, especially towards the inferior end. It is very broad 
throughout, but much compressed from before backwards. At the angle it bends very 
abruptly, the main part of the rib, or that below this point, being almost straight. The 
inner concave border is very sharp, the outer one more rounded. ‘The tubercle is very 
largely developed, forming a great expanded rugged crest at the upper extremity of 
the bone, by which it articulates with the end of the transverse process of the first 
dorsal vertebra. The capitular process is quite rudimentary, being a slight angular 
projection marked off from the tubercle by a shallow depression. It may have had a 
ligamentous union with the rough elevation near the hinder border of the body of the 
seventh cervical vertebra; but there must have been an interval of fully 6 inches 
between them. At the lower end the whole bone is twisted on itself, the anterior 
surface turning outwards, and the inner edge forwards. The size of the bone also is 
increased greatly, not only in breadth, but in thickness—the last alteration mainly 
affecting the inner or anterior part, so that the sharp edge previously mentioned 
becomes quite rounded, and the surface of the truncated inferior extremity is much 
wider at its inner than its outer end. 
The second rib partakes somewhat of the massiveness of the first, though it is con- 
siderably longer, and of very different general form. Its curve is tolerably regular, 
though the principal bend is, as usual, in the neighbourhood of the angle. It is 
flattened from before backwards, and has a sharp internal edge. The tubercle is 
much reduced in size, and presents a broad oval surface for articulation with the 
transverse process of the second dorsal vertebra. The neck is a well-developed com- 
pressed process, tapering towards the apex, where it is somewhat dilated, and must 
have reached very nearly, if not quite, to the small articular surface on the side of the 
body of the first dorsal vertebra. A very prominent crest extends backwards from 
the tubercle, terminating rather abruptly at the angle. ‘This distinguishes the second 
rib from the first, as well as from those that come after it in the series. The outer 
surface is much more regularly convex than that of the first rib. The anterior surface 
gradually becomes external towards the lower end; and the expansion of this part (less 
marked than in the first) affects chiefly the middle of the bone, the truncated end pre- 
senting a regularly oval surface. 
The third rib is longer, but thinner than the second. Its curve is rather wider; it is 
less compressed and wants the prominent sharp inner concave border, and also the crest 
above the angle; its tubercle is less rounded, but rises into a sharp angular process 
surmounting the flat inwardly turned articular surface ; its capitular process is longer 
and more dilated at the end. The inferior extremity is still considerably enlarged, but 
less than in the last. 
The fourth, fifth, and sixth ribs closely resemble the third, and each other; but the 
