354 MH. W. H. FLOWER ON THE OSTEOLOGY OF THE SPEEM-WHALE. 



and 2f" in greatest diameter at the proximal end ; the other is 11" in length, and 2^" 

 in diameter at the same point. 



The ribs of the Caithness and Yorkshire skeletons agree in theii- number and general 

 characters with those of the present specimen. In the former, the two rudimentary 

 eleventh ribs are preserved, and are 13^" and 12^" long respectively, and somewhat 

 stouter than in the Tasmanian Cachalot. In the skeleton at Burton Constable they are 

 not present; but the condition of the ends of the transverse processes of the corre- 

 sponding vertebrae clearly indicate their former existence. In the Sydney skeleton, ten 

 pairs of fully developed ribs are described. The small eleventh pair, if they existed, 

 may easily have escaped observation, especially as the animal was scarcely more than 

 half-grown. 



The skeleton at Paris has fourteen pairs of large ribs, with indications on the trans- 

 verse processes of a fifteenth. Their articular surfaces, as well as the corresponding 

 processes of the vertebrae, are much decayed and broken ; but, as far as can be ascer- 

 tained, they appear to follow each other in a regular and natural sequence, and afford 

 no certain evidence that the skeleton has been artificially compounded. The fii'st pair 

 have rudimentary capitular processes, larger on the left than the right side. These 

 are followed by ten pairs with well-developed capitular processes reaching to the bodies 

 of the vertebrae in the usual way. The last three are connected only with the lower 

 transverse processes, which are strongly developed and hollowed out at the end for 

 their reception. 



In all the true Dolphins [DelpMnidw) the anterior ribs (about half of the series) have 

 long heads, by which they are connected with the body, or root of the arch, of the ver- 

 tebra in front of that to which the tubercle is attached. Near the middle of the series 

 this head suddenly ceases to be developed, and the ribs articulate only to one vertebra, by 

 the tubercle. It will be seen from the preceding description that in the Cachalot the 

 condition of the upper end of the ribs, and their mode of connexion with the vertebi-ae, 

 is quite diiferent. Of the Cetaceans ^vhose osteology is thoroughly known, Hyperoodon 

 comes nearest to Physeter in this respect, as already mentioned when speaking of the 

 transverse processes of the thoracic vertebrae. The form of the first rib of the Cachalot, 

 however, is very peculiar — the absence of a distinct head reaching the body of the 

 vertebra having no counterpart among Toothed Whales, not even in Hyperoodon. 



Sternum. 

 The sternum (PL LX. figs. 3 and 4), is a large, massive bone, though of rather spongy 

 texture. Its general form is roughly triangular, the apex being turned backwards. 

 The broad anterior edge, nearly equal to the sides in length, is tolerably straight. It 

 is composed of three distinct portions — two large anterior lateral pieces, and a small 

 posterior median piece. The former have probably each consisted of an anterior and 

 posterior portion, though the traces of this distinction are well-nigh obliterated. The 



