UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 5, No. 24, pp. 381-390, PI. 40 ANDREW C. LAWSON, Editor 



THE SKULL AND DENTITION 



OF A 



PRIMITIVE ICHTHYOSAURIAN 



FROM THE 



MIDDLE TRIASSIC 



BY 



JOHN C. ME RE I AM. 



CONTENTS. 



PAGE 



Introduction 381 



Diagnostic characters 382 



Dentition 383 



Skull 385 



Affinities 388 



INTRODUCTION. 



The material described in the following paper comprises two 

 specimens which were obtained in the Middle Triassic limestones 

 of West Humboldt Range, Nevada. One of these (no. 9924), 

 showing a portion of the dentition with parts of the lower jaw, 

 was figured and described for inclusion in a recent paper on 

 Triassic Ichthyosauria, 1 but was finally withdrawn, as its syste- 

 matic position did not seem clearly determined. A second spec- 

 imen (no. 9853), which has since been exposed for study, shows 

 the middle portion of a skull, with a dentition similar to that of 

 no. 9924. 



i Merriam, J. ('., Triassic Ichthyosauria, Mem. Univ. Calif., vol. 1, no. 1. 



