712 



ON THE CAUDAL VERTEBRA OE A CETACEAN. 



appear to have been more convex behind than in front, and the 

 transverse width of the centrum, appears to have been greater, about 

 10 - 6 centim. The base of the centrum is narrow, with a median 

 longitudinal depression more marked beneath than in front, but 

 not very conspicuous, and yet sufficient to give the base the appear- 

 ance of being formed of two rounded lateral portions. The basal 

 surface is concave from front to back : it is impossible to state its 

 transverse width in the middle, because there are no lateral limiting 

 lines ; but it exceeds 2| centim. The inferior lateral surfaces are 

 nearly flat from above downward, the concavity being scarcely ap- 

 preciable, but are markedly concave from front to back. The supe- 

 rior lateral surfaces are convex from above downwards (fig. 2), the 

 convexity being least marked in the middle and more marked on the 

 posterior border than on the anterior border. The length of the 

 transverse processes cannot be given, because they are fractured ; but 

 since the fractured end is only half a centim. thick, and 4*7 centim. 

 wide, it was presumably short. This process is perforated vertically 

 by an oval foramen (fig.l) which is 7millim. long and 5 millim. wide. 

 Its anterior margin is distant 3*4 centim. from the anterior border 

 of the vertebra ; and the posterior margin is 2-5 centim. from the 

 posterior border. On the left side the foramen appears to be a little 

 smaller, and nearer to the middle of the centrum. 



The neural arch is small, depressed, placed anteriorly so as somewhat 

 to overhang the centrum (fig. 1). It has a scarcely appreciable neural 

 spine (fig. 2); but its posterior margin is broken away. The sides of the 

 neural arch converge posteriorly, so that the transverse measurement 

 behind, as preserved, is 3 centim. The antero-posterior measurement 

 of the base of the neural arch is rather more than 4 centim. (fig. 2). 

 The anterior zygapophyses, if such existed, are- broken away: and the 

 extreme transverse width of the neural arch in front (fig. 3), which is 

 obviously less than its width when perfect, is about 5 centim. The 

 sides of the arch are directed upward and outward ; and the neur- 

 apophyses are compressed. The canal for the spinal cord is wider in 

 front than behind, and higher behind than in front. The transverse 

 measurement in front is 2*7 centim. The height in front is 1*4 

 centim. The height behind is about 1*6, as preserved, and the width 

 fully 2 centim. The neural canal is concave from front to back, 

 and contains several nutritive foramina. Two are placed near 

 to the anterior margin, and one in the middle line behind the 

 middle of the centrum. The superior surface of the neural arch was 

 probably notched in front, where it was concave from side to side ; 

 it was inclined backward, where the sides converge, and where it is 

 divided mesially by the faint indication of a neural spine (fig. 1). 



