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University of California Publications. [Geology 



The posterior dorsal and the caudal vertebrae are character- 

 ized by very high, slender neural arches. The arches stand nearly 

 erect over the posterior dorsal and anterior caudal regions, but 

 are suddenly turned sharply forward near the middle of the 



Fig. 5. Mixosaurus( ?) nordenskioldii (Hulke). A portion of the dor- 

 sal and caudal series, X %. (After Wiman). 



bend in the tail. The centra of the caudal region are consider- 

 ably increased in both relative and absolute height behind the 

 middle of the bend, and are very noticeably flattened laterally. 



In a reconstruction of Mixosaurus nordenskioldii published 

 by Wiman (fig. 6) the expansion of the caudal fin is represented 



Fig. 6. Restoration of Mixosaurus (?) nordenskioldii (Hulke). (After 

 Wiman ) . 



as widest at a point only a short distance posterior to the pelvic 

 limb. Wiman 's reconstruction is apparently based on the pro- 

 portions of a specimen showing the posterior dorsal and caudal 

 region as reproduced in figure five. In this specimen as figured 

 there is an extraordinarily sudden lengthening of the neural 



