352 ME. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-WHALE. 



The first rib (PI. LX. fig. 2) is very difiierent 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 ofi" 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 mner or anterior part, so that the sharp edge previously m.entioned 

 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 diff'erent 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 thu'd 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 fiat inwardly turned articular surface ; its capitular process is longer 

 and more dilated at the end. The inferior extremity is still considerably enlarged, but 

 less thaii in the last. 



The fourth, fifth, and sixth ribs closely resemble the third, and each other; but the 



