71' 



University of California Publications. 



[Geology 



is coarser than in any other species of Acrodus known to the 

 writer. Only one of the serrations is connected with the ridges 

 higher np on the crown. The middle of the crown is much wider 

 than the ends, which narrow gradually. The longitudinal crest 

 on the crown is a very narrow but well defined ridge which con- 

 tinues unbroken along the entire surface of the crown. Imme- 

 diately above the serrated lateral margin the crown is smooth. 

 Half way up the side of the tooth a series of delicate ridges arises 

 and runs into the longitudinal crest. 



ACRODUS OREODONTUS, 11. Sp. 

 PI. 7, figs. 1, 2. 



Type specimen No. 10251, Univ. Calif. Col. Vert. Palae. From the upper 

 part of the Middle Triassie, Cottonwood Canon, West Humboldt Range, 

 Nevada. 



The teeth are elongated, depressed, with a median prominence, 

 and a well defined median ridge. No lateral prominences are 

 present. The coronal contour is strongly rounded. Coarse wrin- 

 kles converge toward the apex and the longitudinal crest. This 

 convergence is more noticeable on one surface of the tooth. On 

 this surface the distance from the base to the lower edge of the 

 crown is about half the same distance on the other surface. This 

 surface is more coarsely ornamented than the opposite side. The 

 straight longitudinal crest is situated medially on the crown. 



HYBODUS NEVADENSIS, 11. sp. 

 PI. 7, fig. 3. 



Type specimen, one detached tooth, No. 10254, Univ. Calif. Col. Vert. 

 Palae. From the upper part of Middle Triassie, Cottonwood Canon, West 

 Humboldt Eange, Nevada. 



Tooth cuspidate, crown relatively low and vertically striated, 

 with one principal elevation situated a little away from the 

 middle of the tooth. The lateral prominences are two in number. 

 These prominences are well defined and sharply conical. No lat- 

 eral denticles are present on the opposite side. The root is sepa- 

 rated from the crown by a deep grove. The type specimen prob- 

 ably belonged to the symphyseal portion of the jaw, as it shows a 

 high, robust, principal cone. 



