ANATOMY OF MEGAPTERA LONGIMANA. 115 



The arch rises to the base of the spine, which projects about 

 1 inch as a median crest, extending the whole length of the 

 arch. It has a curved form, not unlike that of the spine of the 

 atlas, but the greater prominence on the anterior half is more 

 marked than on the atlas. The top of the spine is 1J inch 

 above the level of the lateral ridges. 



Posterior Aspect of the Body of the Axis. The greater 

 diminution on the posterior surface of the body of the axis in 

 Megaptera is remarkable. On the anterior aspect the total 

 width of the body, to the outer edge of the articular surfaces, was 

 noted above as only \ inch less in Megaptera (13J inches) than 

 in the B. musculus. On the posterior aspect, the width of the 

 body is in the B. musculus 11 J inches, in Megaptera only 9J. 

 This is a change to the lesser width of the bodies of the five 

 posterior cervical vertebrae in Megaptera compared with B. 

 musculus. 



33. THE FIVE POSTERIOR CERVICAL VERTEBRA. Bodies. 

 The measurements are given in Table II. The forward diminu- 

 tion in breadth (already noted with the bodies of the lumbar 

 and dorsal vertebrae) ceases with the 7th cervical. The breadth 

 is then the same (8J inches) on to the 3rd cervical, where it 

 becomes 9J. The forward diminution in height is arrested from 

 the 1st dorsal to the 5th cervical, on which the height exceeds 

 the 7 inches, and diminution is resumed on the 4th and 3rd 

 cervical. The forward diminution in length goes on steadily 

 along the neck, from 2f inches on the 1st dorsal to 1J inch 

 on the 3rd cervical. 



[In B. musculus (Table III.) the forward diminution in breadth 

 ceases on the 7th dorsal. From 9f inches there the breadth has 

 increased at the 7th cervical to Hi, and at the 3rd cervical to ll 



o J o 



inches. The forward diminution in height ceases at the 5th dorsal ; 

 from there to the 7th and 6th cervical the height has increased from 

 7 inches to 7|, and thence to the 3rd cervical has again diminished 

 to 7 inches. The forward diminution in length is continued in the 

 neck, from 3i inches on the 1st dorsal to 24 on the 7th cervical, and 



o 



to 1 j on the 4th and 3rd.] 



The contrast between the bodies of the cervical vertebrae in 

 Megaptera and B. musculus is, in Megaptera, their less breadth 

 compared with the height. Taking the 4th cervical, these 

 measurements are, in Megaptera, breadth 8J inches, height 7; 



