UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 11, No. 4, pp. 433-435, 2 text-figures May 9, 1919 



A CESTRACIONT SPINE FROM THE MIDDLE 



TRIASSIC OF NEVADA yeoman 



r* ma*- ■ 



PIEIE DAVIDSON 



Among the vertebrate materials collected in the Middle Triassic 

 beds exposed in the West Humboldt Range of Nevada there is a single 

 fairly preserved spine of a cestraciont. Isolated spines resembling 

 this specimen have been found in the Devonian, Sub-Carboniferous 

 and Coal Measures of this country. One specimen, Cosmacanthus 

 elcgans, from the Lower Triassic of Idaho has been described by 

 Evans. 1 Cestraciont teeth have been described from the Middle and 

 Upper Triassic of California and Nevada by Miss Wemple 2 and by 

 Bryant. 3 The teeth described by Miss "Wemple represent the same 

 locality as the specimen described here, which is a new species. 



COSMACANTHUS HUMBOLDTENSIS, n. sp. 



Type specimen no. 9162, Univ. Calif. Coll. Vert. Palae. From the upper part 

 of the Middle Triassic, Straight Canon, West Humboldt Range, Nevada. 



The spine (figs. 1 and 2) is of medium size, tapering quite abruptly 

 with a slight curve backward. The greatest length is 59.5 mm. and 

 its greatest width 12 mm. It is bilaterally symmetrical and is made 

 up of a long plain inserted portion which has a deep furrow poste- 

 riorly, and a short exserted portion which is partly covered by small 

 closely set sculptured tubercles. Most of the projecting part is closed 

 posteriorly and the furrow extends into it as the medullary cavity. 



1 Evans, H. M., A new cestraciont spine from the Lower Triassic of Idaho, 

 Univ. Calif. Publ. Bull. Dept. Geol., vol. 3, pp. 397-402, 1 pi., 1904. 



2 Wemple, E. M., New cestraciont teeth from the West American Triassic, 

 Univ. Calif. Publ. Bull. Dept. Geol., vol. 5, pp. 71-73, 1 pi., 1906. 



3 Bryant, H. O, Teeth of a cestraciont shark, Univ. Calif. Publ. Bull. Dept. 

 Geol., vol. 8, pp. 27-30, 1914. 



