150 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA. 



concave, but relative to the whole area the extent of the concavity was small, 

 and for some distance below the neural canal the surface was nearly plane. 



The vertebrae present in the series of eight centra Hulke considered as 

 representing the posterior dorsal or the anterior caudal region. The writer 

 (1902, 2, p. 88) suggested that they resemble the posterior dorsals of Shas- 

 tasaurus. The narrow form of the centra favors somewhat Hulke 's suggestion 

 regarding their position in the anterior caudal region, but the long, narrow rib 

 articulation is more like that of posterior dorsals in the shastasaurine group. 

 The limited area of deep concavity on the anterior and posterior faces suggests 

 the characters of Cymbospondylus /x'friini.s, in which the pos- 

 terior dorsals are also relatively narrow (pi. 9, figs. 2 and 3) . 

 The three consecutive centra of the second vertebral series 

 were much compressed laterally and had short rib facets. 

 They may have represented caudals. 



Judging from the available material of this species it lie- 

 longs in the shastasaurine group. It is not possible to make 

 certain of the genus to which it belongs. The suggestion of 

 Yakowlew and the writer regarding its affinities with Shasta- 

 saurus were justified in the light of the information at hand, 

 but with a better knowledge of the genus Cwribospondylus it 



Fig. 150. Cymbospondy- ,, 7 . -111 i i J.T -.LI' 



hU(t) poiaris (Hulke) appears that poians might be placed in that genus with more 

 (After' Yntw^ reason than could be advanced for referring it to 



SOUTHS. 



CYMBOSPONDYLUS ( ?) NATANS, n. sp. 



A perfectly preserved humerus (no. 9873, see pi. 13, figs, la and 1ft) from 

 the Triassic of the West Humboldt Range of Nevada differs so much from the 

 humerus of Cymbospondylus petrinus that its characters are not covered by the 

 description of that species, and possibly not even by the genus Cymbospondy- 

 lus. In some respects this specimen approaches the genus Mixosaurus more 

 closely than does the typical Cymbospondylus. 



As indicated by the following measurements the humerus is relatively short 

 and broad and represents a somewhat smaller form than the typical Cymbos- 

 pondylus pet tin HH. 



MEASUREMENTS OP HUMERUS, NO. 9873. 



Greatest length 53 mm. 



Greatest width of distal end 38 



Width of median or shaft region 31 



Greatest thickness of distal end ... .. 11 



