380 Mr. C. Forster-Cooper on Thaumastotlierium osborni. 



horse. The dorsal and ventral ridges are but little 

 marked. The vertebrarterial canal is very large and 

 shows a peculiar feature in the way it excavates the 

 centrum. This modification is also shown by the 

 atlas, and still better in the following vertebra, 

 which is 

 (7) A later cervical (fig. 5, front view). This bone differs 

 from that just described in having a less great fore- 

 and-aft depth, the proportions being otherwise much 

 the same. One side being broken away, it has been 

 possible to trace out the course of the vertebrarterial 

 canal, which shows a very curious feature in expanding 

 into a large "cave" in the body of the vertebra to 

 such an extent that the bone between the expansions 

 of each side is reduced to a thin vertical partition 

 running the length of the bone. This structure is 

 shown in the accompanying diagram, which is a plan 

 of a section taken transversely through the vertebra. 



Another similar vertebra, which is in process of 

 being prepared, shows the same feature, probably a 

 method of saving weight. 



Fir. 7. 



(H) The remaining vertebra (fig. 7) is apparently an anterior 

 thoracic, it measures 42 cm. in width across the 

 posterior zygapophyses. The neural spine is rather 

 peculiar in being very broad and Hat, the upper border 

 of the spine is broken away, but it does not seem to 

 have been very much higher. 



