PEOFESSOE FLOWER ON EISSO'S DOLPHIN. 7 



In height they gradually increase from 2 inches (first) to 2-4 inches (nineteenth) ; in 

 breadth they increase from 2-3 inches (first) to 2-4 inches (nineteenth) at the articular 

 ends. The sixth, seventh, and eighth have the highest spines, viz. 6*4 inches from the 

 upper surface of the body of the vertebra to the tip of the spine — the height of the first 

 being 6 inches, that of the last 4 - 3 inches. The spines are long, slender, upright, and 

 devoid of metapophyses. The transverse processes gradually diminish from the first 

 (where the breadth of the vertebra between the tips of the processes is 11 '2 inches) to 

 the last (where the same measurement is but 7 - 5 inches) ; they are very nearly equal in 

 antero-posterior breadth throughout, viz. 0'9 of an inch; and they arise from rather 

 nearer the front than the hinder end of the body ; but this is less marked in the pos- 

 terior than in the anterior portion of the series. 



I have, as usual, reckoned as the first caudal vertebra that which bears at the hinder 

 end of its body the first chevron bone. The bodies of these increase in length from the 

 first (which is T4 inch) to the sixteenth and seventeenth (which are 2 inches), after which 

 they again diminish. In height they do not differ greatly, until beyond the eighteenth, 

 when they rapidly decrease. They begin to diminish in breadth after the eleventh. 

 The lateral compression characteristic of this part of the vertebral column of Cetacea 

 continues until the twentieth vertebra; the twenty-second is the first of the series of 

 broad, depressed, terminal vertebrae, the twenty-first being of transitional form. The 

 spinal canal ceases at the nineteenth caudal vertebra. The transverse process is reduced 

 to a low ridge on the fourteenth, and disappears altogether on the fifteenth. The 

 vertical vascular canals first appear in the middle of the base of the transverse process 

 of the fifth, though small, and on the right side only; on the sixth they are present on 

 both sides, and they continue as far as the penultimate vertebra. The terminal vertebra 

 is a small, triangular nodule, very inferior in width to that which precedes it. 



The chevron bones present are twenty in number, all having the two lateral halves 

 united. It is not improbable that some additional ones from the hinder end of the series 

 may have been lost in macerating the skeleton. The first two are small, with no spines 

 developed beyond the union of the laminse. The third shows a sudden increase in 

 length, which augments in each succeeding one until the seventh, after which they 

 diminish in length, but are more expanded in the antero-posterior direction. 



There are twelve pairs of vertebral ribs, all of which, except the first three or four, 

 are very slender. The anterior six pairs have long necks, reaching in each case to the 

 articular surface on the side of the vertebra in front of that to which the tubercle is 

 attached. The seventh presents, on both sides, a peculiar arrangement. The rib is not 

 developed inwards beyond the tubercle, which articulates (as do all the posterior ribs) 

 with the end of the transverse process of the corresponding vertebra ; but, detached from 

 the rib, and fused with the under surface of the transverse process of the vertebra, is a 

 strong spiculum of bone T4 inch long, with its free end pointing forwards, downwards, 

 and inwards, and reaching to within half an inch of the before-mentioned tubercle on 



