DISTRIBUTION OF JURASSIC AMMONITES. Ill 



probably in the southern portion of the Star Peak range. There are also 

 fossils in the collection of the mining bureau at San Francisco labeled 

 as having been gathered in the Santa Fe district, Esmeralda county, 

 Nevada, and Inyo county, California. These would not be worth men- 

 tioning were they not reported from places lying in the direction of the 

 general strike of the Jurassic strata and also in perfect accord with the 

 presence of Amioceras humboldti. One species is a form of Vermiceras 

 allied to 1". conybeari of the faunas of the lower Lias in Europe, which I 

 propose to name V. crossmani* The second fossil, from Inyo county, 

 was considered by me in the work already quoted to be identical with 

 Amioceras humboldti, hut a reexamination of the same specimens made 

 in the summer of 1891 has satisfied me that this was an error. The pike 

 are more closely crowded, and there are slight constrictions at intervals 

 on the whorls of the nealogic (adolescent) stages. These disappear later, 

 giving way to slightly arcuate costa', which also differ from those of Amio- 

 ceras humboldti. I therefore propose for this peculiar form the name of 

 Amioceras woodhulli.i These facts all tend to the conclusion that the 

 lower Lias, having certain forms of undeniable European fades, occurs 

 in western and southwestern Nevada and perhaps in California east of 

 the crests of the Sierra. 



It is impracticable at present to discuss the relations of these faunas 

 with those of the Lias on the western slopes of the Sierra Nevada further 

 than to say that they are undeniably older than those found at mount 

 Jura. 



It is obvious, from all of these facts and others that might be men- 

 tioned, that the Jura occurs in widely separated patches, and that so far 

 ;is now known mount Jura exhibits a larger number of fragments of the 

 series of the Jurassic system than any other known locality in the United 

 States, and that it was the best at which to make the first attempt to 

 study this system in detail. 



♦ The type is number 4989, collection of the State Mining Bureau, San Francisco, California, eol- 

 iected by J. E. Crossman. There is one specimen with the. internal whorls and part of a living 



chambering I condition, and two large fragments more compressed. It is ;i species having 



n i line roiis whorls, as in tin' more generalized forms of the genus, straight numerous costse without 

 tubercles on Hi'' geniculse, but the latter are prominent cm the outer whorl anil look us if they 

 might have tubercles in later >t :i o->> -. The abdomen is channeled ami keeled. 



fThe typo i- in the collection of the State Mining Bureau, San Francisco; number 7642, Inyo 

 i ounty, California, collected by D. S. Woodhull. 



I.\ I I' i"i 801 . A m.. Vni . :; 1891 . 



