318 



University of California Publications. 



[Geology 



sible a more satisfactory determination of the nature of the 

 saurian forms represented in this fauna than had previously 

 been possible. The results of a study of the collection by Wiman 3 

 form a most interesting and important contribution to our knowl- 

 edge of this group, and materially assist in comparison of the 

 Spitzbergen Triassic with that of the rest of the world. 



OCCURRENCE 



The ichthyosaurian remains from Spitzbergen are described 

 by Wiman as occurring in two horizons of the middle Trias. 

 The upper horizon is in the Daonella shales, and contains abund- 

 ant specimens of the ammonite genus Ptychites. The saurian 

 collection from the upper beds comprises Mixasaurus(f) norden- 

 skioldii (Hulke), and Pessosaurus polar is (Hulke). 



The lower saurian horizon is about three hundred and fifty 

 feet below the upper beds. Below it is an ammonite fauna in- 

 cluding Ceratites polaris. At this horizon two saurian forms 

 were found, which are described as Pessopteryx nisseri, n. gen. 

 and sp., and P. minor. A short distance below the lower horizon 

 a number of large ichthyosaur teeth were found. 



Excepting the specimens representing M. (?) nordenskioldii, 

 all of the material from Spitzbergen unfortunately consists of 

 scattered or isolated bones. The M. (?) nordenskioldii specimens 

 are much better preserved than the others, and in some cases 

 show considerable connected parts of skeletons. 



MIXOSAURUS(?) NORDENSKIOLDII (Hulke) 

 Both Mixosaurus ( ? ) nordenskioldii and Pessosaurus polaris 

 were first described by Hulke in 1873 under the name of Ichthyo- 

 saurus. Since that time it has been clear to several writers that 

 they could not remain in that genus, and various suggestions 

 as to their possible relationships have been made by Dames, 4 

 Yakowlew/' and Merriam." 



3 Wiman, Carl, Ichthyosaurier aus der Trias Spitzbergens, Bull. Geol. 

 Inst. Upsala, vol. 10, pp. 124-148. 1910. 



i Dames, W., Sitzb. d. Acad. d. Wiss. Berlin, 1895, p. 1045. 



s Yakowlew, N., Verb. d. Kais. Russ. Min. Ges. Bd. 40, p. 179. 1902. 



6 Merriam, J. O, Univ. Calif. Publ. Bull. Dept. Geol. vol. 3, pp. 87, 88. 

 1902. 



