PLATANISTA. 533 



posterior zygapophyses are close to the base of the spinous process, their facets looking 

 outwards and very slightly downwards. The spinous processes of the first are higher 

 than any of the other dorsal vertebrae, and they have a considerable backward course 

 and are closely opposed to each other. The third is generally distinguished by its 

 anterior superior angle being projected forwards and upwards in a recurved manner. 

 The transverse breadth of the bodies increases from the first to the fourth, the vertical 

 height diminishing, so that the posterior articular surface of the fourth dorsal is trans- 

 versely oval ; whereas the anterior surface of the fixst is quadrangular, but a very little 

 broader than high. The under surfaces of the body of the first three are marked 

 by a more or less distinct longitudinal furrow as in the last cervical. On the second, 

 third, and fourth there is a distinct tubercular swelling where the head of the rib rests 

 on the posterior margin of the bodies of the vertebrse. The articular surfaces 

 on the transverse processes are large and longitudinally elongate, and in the first 

 distiactly concave. 



The distinctive features of the six remaining dorsal vertebrse are the presence 

 of strong metapophyses, short transverse processes, and broad spinous processes 

 directed forwards, except in the case of the fifth and sixth, which have a slight back- 

 ward course. In the fifth, the transverse process is so shortened that it appears merely 

 as an elongated oval facet on the thickened external sm-face of the metapophysis, 

 the thickening itself being the true transverse process which is obscured by the 

 former. On the sixth, the transverse process attains its least development and 

 appears as a small expanded ridge. There is a rough surface at its inferior margin to 

 which the head of the rib is articulated, and a similar and larger surface on the 

 external posterior margin of the body. From the seventh to the ninth vertebrae, the 

 transverse processes increase very little in size, but become lower and lower in posi- 

 tion. In the tenth vertebra, the rib is suddenly transferred to a transverse process as 

 long as the centrum, but compressed from above downwards. The metapophyses 

 become higher and higher in their position as they are traced backwards, and the 

 zygapophyses in the last dorsal become placed at the base of the spinous process, 

 the posterior pair having a more and more outward aspect and the anterior looking 

 directly inwards. The metapophyses are thick powerful processes directed for- 

 wards, upwards, and outwards. The spinous processes increase in antero-posterior 

 expansion from the seventh to the tenth, the last being much the broadest and higher 

 than those before it. The last four dorsal vertebrae have their spinous processes 

 curved forwards. The bodies are aU broad and long with a transversely oval section, 

 and on the under surface they are concave from before backwards but transversely 

 curved between the transverse processes. The neural canal in the tenth is 

 broader than high, but its capacity is less than one-half of the canal in the first 

 dorsal. 



Lwmbar vertebrce. — The seven or eight, as the case may be, are distinguished by 

 their enormously developed transverse processes which attain their maximum in 

 the third, fourth, and fifth, but at the same time these processes occur strongly 

 developed along the first half of the caudal region. The zygapophyses wholly dis- 



