510 DE. J. MUEIE ON THE AJSTATOlNrS' OP THE SEA-LION. 



but short. The dorsal Tertebrse present no striking difference from those of Seals 

 generally. Gradually narrowing, the dorsals merge into the lumbar vertebrae, which 

 are Hkewise larger, but not specially characterized from other Phocine genera. In 

 computing the presence of four sacral vertebrae, I am guided partly by the nervous dis- 

 tribution and partly by the fact that the said number bears closest resemblance to each 

 other of the series. Together they are distinguished by their raking neural arches and 

 spines, subequal in length, and lying upon each other almost in an imbricated manner. 

 The foremost has the largest body, the modified great flat-surfaced transverse processes 

 forming a sacro-iliac synchondrosis, a facet of the second assisting. The bodies of the 

 2nd, 3rd, and 4th are carinate, but, nevertheless, have not the depth of the 1st. The 

 pedicles of their transverse processes are uncommonly squat, a retral bar, however, 

 enclosing an intertransverse foramen. 



In our adult male animal under consideration, there are eight caudal vertebrae re- 

 markably movable upon each other by the intervention of thick interarticular fibro- 

 cartilaginous disks. The vertebrae diminish regularly from the iii'st to the last, which 

 is of very small size, and but incompletely ossified. The first two have each backwardly 

 directed spinous processes. The third has two imperfectly formed thick laminar eleva- 

 tions, but no spine. All three of these vertebrae have well-developed transverse 

 processes. From the fourth to the eighth caudal element there are no spinous or 

 transverse processes, slightly raised elevation of the bone alone representing these 

 structures. 



b. The Ribs. — Of the fifteen pairs of ribs, the 1st, 2nd, and 3rd are the shortest, then 

 follows the 15th. From the 4th backwards to the 9th and 10th, there is a gradual 

 increase in length, from which they decrease. as they go backwards. 



The subjoined Table gives the respective costal lengths in the young and adult 

 animals. The measurements in each are from the angle to the costal tip : — 



Eibs. Young. Adult (Z. S. sp.). 



1st 



and 



3rd 



4th 



6th 



6th 



7th 



8th 



The first rib has a stout roimdish straight body, with a very slight antero-posterior 

 compression. The neck, set almost at a right angle to the body of the rib, is thick, 

 and markedly grooved in front and behind. The capitulum is of moderate size ; it 

 articulates with the anterior part of the body of the first dorsal vertebra, barely im- 

 pinging against the intervertebral cartilage. The prominent tubercle, and its articular 



