UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 5, No. 4, pp. 71-73, PI. 7 ANDREW C. LAWSON, Editor 



NEW CESTRACIONT TEETH FROM THE 

 WEST -AMERICAN TRIASSIC. 



BY 



Edna M. Wemple. 



CONTENTS. page 



Introduction 71 



Acrodus alexandrae, n. sp : 71 



Acrodus oreodontus, n. sp 72 



Hybodus nevadensis, n. sp 72 



Hybodus shastensis, n. sp 73 



INTRODUCTION. 



In the summer of 1902 a palaeontological expedition from the 

 University of California obtained a number of eestraciont teeth 

 in the Middle Triassic beds exposed in the West Humboldt Range 

 of Nevada. A second expedition in 1905 found additional mate- 

 rial at other localities in the same beds. Teeth of these types are 

 known to occur elsewhere at horizons from the Middle Triassic 

 to the Upper Cretaceous, but as yet these specimens, with a few 

 fragmentary teeth from Shasta County, California, appear to be 

 the only eestracionts known in the Triassic of North America. 

 All of the specimens obtained seem to represent new species, 

 which are probably to be considered as characteristic fossils of 

 this horizon of the Triassic. 



ACRODUS ALEXANDRAE, n. sp. 



PI. 7, figs. 5 and 6. 



Type specimen, one detached tooth, No. 9874, Univ. Calif. Col. Vert. 

 Palae. From the upper part of the Middle Triassic, Fisher Canon, West 

 Humboldt Range, Nevada. 



The tooth is large, elongated, and with a faint median keel. 

 The crown is low and wider than the root. The overhanging mar- 

 gins are very deeply and sharply serrated. This ornamentation 



