v.] SIRENIA. 51 



have vety long and slender transverse processes directed 

 downwards and forwards and widening at their extremities ; 

 long metapophyses projecting upwards and forwards, small 

 anapophyses, and remarkably long, single, compressed 

 median hypapophyses. These latter are not found in the 

 Rodentia generally. 



In the Ungulata, the bodies of the trunk vertebrae are 

 generally slightly opislhoccelous; The spinous processes in 

 the anterior thoracic region are exceedingly high and com- 

 pressed. The transverse processes of the lumbar vertebra; 

 are long, flattened, and project horizontally outwards or 

 slightly forwards from the arch. The metapophyses are 

 moderately developed, and there are no anapophyses. The 

 canals for the exit of the spinal nerves frequently pierce the 

 pedicle of the neural arch. 



In the Artiodactyle sub-order the number of thoracic and 

 lumbar vertebrae together is always 19, though the former 

 may vary from 12 to 15. Among the Perissodactyles the 

 number 23 is equally constant, the Horse and Tapir having 

 18, and the Rhinoceros 19 thoracic vertebrae. 



Some species of Hyrax have as many as 22 thoracic and 

 8 lum.bar vertebrae, making altogether 30, the highest num- 

 ber in any terrestrial Mammal 



The Elephants have 23 in all, 19 or 20 of which bear ribs. 



In the order Sirenia, the thoracic vertebrae are numerous 

 and the lumbar very few ; thus the Dugong {Halicore) has 

 19 thoracic and 4 lumbar, and the Manati {Ma?iatus) 17 and 

 2. The bodies are rather triangular, being compressed and 

 keeled below, and in the young state have no distinctly 

 ossified terminal epiphyses. The bodies of all the thoracic 

 vertebrae bear articular facets for the heads of the ribs. 

 The spinous processes are not very high, but the zyga- 

 pophyses are well developed throughout the series. The 



E 2 



