410 CETACEA. 



that the chief peculiarities presented by the cervical vertebrae of this genus are 

 confined to the united 1st and 2nd cervical vertebrae and to the imperfection of 

 some of the neural arches. The measurements of united atlas and axis : — 



Inches. 



Across transverse processes of atlas 4*20 



„ anterior border of occipital facets 3'93 



Depth through anterior r . . 1"62 



Antero-posterior length of centrum 1'36 



„ breadth of laminae of neural arch above posterior zygapophyses . . . 1"15 



Height of neural arch anteriorly 1"25 



Viewing the remaining vertebrae as a whole, they do not present any very striking 

 features. The spinous processes of the dorsal region are moderately developed and back- 

 wardly directed, but in the 1st dorsal, as I have pointed out, the neural laminae are 

 sometimes not united, and even in the 2nd, 3rd, and 4th dorsal, the laminae of opposite 

 sides are posteriorly separated from each other by an incision, and this may be traced 

 more or less to the 8th dorsal. The tips also of the spinous processes of the 4th to the 

 10th dorsal manifest a tendency to bifurcate. The body of the 1st dorsal is about 

 one-third thicker than that of the last cervical, and the vertebrae behind it gradually 

 increase in size to the 10th dorsal, the latter having an antero-posterior thickness of 

 1'''95, which is the maximum length attained by the body of any vertebra. 

 External to the anterior zygapophysis on the 5th dorsal there are distinct in- 

 dications of a mammillary process, and its presence indicates the vertebra in 

 which there is the first appearance of a tendency in the anterior and posterior 

 zygapophyses to shift their position upwards along the neural laminae to the base 

 of the spinous processes. On the 7th dorsal the anterior and posterior zygapophyses 

 have become wholly transferred to the base of the spinous process of that vertebra. 

 The anterior zygapophyses diminish in length from the 10th dorsal. The transverse 

 processes of the dorsal vertebrae have the usual Cetacean character. 



In the lumbar vertebrae the neural canal rapidly diminishes in diameter from 

 0""89 to 0"*38, and also in height, the height of the canal in the first of these vertebrae 

 being 1"-16 and in the last 0"'95. The spinous processes are directed backwards, their 

 anterior margins being concave and their posterior margins convex. They increase 

 in length to the 8th, but diminish in length and in breadth from the 10th dorsal to the 

 last caudal, with a trace of a spinous process, the diminution in the latter dimension 

 being very gradual. In the 8th lumbar the tip of the spinous process is 1"'60 

 above the level of the posterior ridge from the zygapophysis, and the latter 

 point is r'"40 above the body of the vertebra. The processes are relatively consider- 

 ably shorter than in 'Fhoccena. The anterior zygapophyses retain their conjoint 

 bifurcate character as far as the 9th lumbar, clasping the posterior zygapophyses 

 of the 8th segment, but in the 10th lumbar they suddenly become reduced in 

 dimension to a rounded plate not touching the vertebra in front of it, and all trace 

 of a mammillary process disappears on the last lumbar. 



The transverse process of the first lumbar is about one-fourth longer than the 

 transverse process of the last dorsal, and is much more backwardly directed. The 

 processes gradually increase in length to the 5th lumbar, becoming more and more 



