182 



ISAL^NOPTERID.E, 



and the spines are high. In the second lumbar vertebra, which is 

 the largest, the extreme width is 40" and the height 29". 



Fig. 42. Atlas ; imder surface. Fig. 43. Axis : anterior surface. 



" The ribs generally are slender, the first much shorter, broader, 

 and flatter than any of the others. The vertebral end of this is 

 split to the depth of about G" into two flat broad plates, of which 

 the anterior is slightly the longer ; this brings their articular sur- 

 faces, when the rib is placed in its natural position (?'. e. somewhat 

 sloping backwards), exactly on a level, and proves that they must 

 have articulated with the equal transverse processes of the seventh 

 cervical and first dorsal vertebra), and not with those of the latter 

 and the second dorsal vertebra, which is 1^ inch shorter. This rib 

 is 321" i'l length in a straight line, 4^" wide at the middle, and 8" 

 at the lower end ; in thickness at the middle it is l"-2. Its general 

 form closely resembles the figure given by Dr. Gray (P. Z. S. 18(J4, 

 ]). 224) from a specimen in the Museum of the lioyal College of 

 ISurgeons, but it is rather broader in proportion to the length. The 

 second, third, and fourth ribs have large articular heads and only 



