THE NORTHERN SEA-COW 1 67 



collection, presented this cast to his English col- 

 leagues in I 876. 



The small skull of the rhytina is remarkable for the 

 strong- development of the nasal bones, which in 

 living sirenians are mere rudiments ; the premaxillae 

 have a downward curve as in recent forms. So 

 loosely were the sutures united in the London speci- 

 men that it was found possible to take a gelatine 

 cast of the brain cavity, as Dr. Brandt had done in 

 a previous instance. The neck, though short, still 

 retains the normal mammalian number — seven — of 

 cervical vertebra ; the sternum, or breast bone, is 

 composed of three pieces, and there are nineteen 

 pairs of ribs. The bones of the skeleton are strong 

 and massive, the ribs being actually used by the 

 natives for carvingf or as sledge-runners. The 

 vertebrae immediately above the root of the tail are 

 not fused into a single mass or sacrum, since 

 such an arrangement would have inconvenienced an 

 animal which, like its living congeners, also moved 

 by freely flexing the tail. Steller {fide Brandt) dis- 

 tinctly said " Motus organon essentiale autem pinna 

 caudalis praebuit'' and again "Caudae motu versus 

 dorsum et ventrem autem corpus impetuosissime 

 propellebant." The manatee acquired by the Zoo- 

 logical Society in August, 1875 — the first living 

 specimen in England— similarly moved the tail up 

 and down, not laterally as in seals: hence the value of 

 a perfectly mobile sacrum will be apparent. From 



