AESINOITHEEIUM. 



31 



portion the centrum may be nearly twice as wide as it is high ; at the same time 

 it becomes somewhat more elongated. The neural border of the centrum is 

 straight and the neural arch is low and wide. The zygapophysial surfaces are 

 cylindrical and the neural spine is low and projects considerably behind the centrum, 

 while at the same time the anterior border of the arch leaves the anterior half 

 of the neural surface of the centrum exposed. The transverse processes are broad 

 from before backwards, and in the anterior region they are narrow from above 

 downwards, but as they are followed backwards they become larger and more massive. 

 In the whole of the large collection of vertebrae in the Museum at Cairo there 

 is not a single example of the sacrum, nor does any such occur in the collection 

 in the British Museum. On the other hand, there are a considerable number of 

 vertebrae of the form shown in text-iig. 14: these greatly resemble the lumbar 

 vertebrae, except that the lateral processes are very large and massive, and bear 

 at their extremities broad, roughened, nearly triangular surfaces (U.S.), apparently 



Text-fig. 14. 



a.z. 



Sacral (?) vertebra of Ardnoiiherium zitteli : A, from front ; B, from right side. 

 a.z., anterior zygapophysis ; n.sp., neural spine ; il.s., iliac surface. 



for union with the ilium. These vertebrae are believed to be the anterior sacrals. 

 Another somewhat different type was probably the second sacral : in this the 

 centrum is even more depressed than in the last, and its ventral surface is almost 

 in the same plane as the ventral surface of the lateral processes, which are very 

 long and terminate in a surface which looks somewhat backwards. The fact that, 

 so far as at present known, the sacrals do not unite as usual to form a sacrum is 

 especially remarkable in an animal of such size and weight. Of course, it is possible 

 that a true sacrum may yet be found, but considering the usual solidity of that 

 structure it is very curious that in so large a collection no specimen should occur, 

 while a score or more examples of the atlas and axis have been obtained. 



The anterior caudals have a very depressed centrum, with broad, flat, rather long, 

 transverse processes. The neural arch is low and situated on the posterior half of 

 the centrum. Further back the caudal centra become more cylindrical, with short 



