Geol.— Vol. I.] SMITH— COMPARATIVE STRATIGRAPHY. 367 



never found in it. So far as can be judged from our 

 present knowledge, the Upper Triassic faunas of California 

 are more intimately related to the Alpine than to the 

 Himalayan species ; but this is probably due to defective 

 information, for the Indian region would seem to have been 

 the most natural and probable connection between the 

 American and the Alpine Trias. 



The uppermost marine Trias, the Noric horizon, is rep- 

 resented in the Pseudomonotis beds of Shasta and Plumas 

 counties, California, and in the West Humboldt Range of 

 Nevada. The characteristic forms of this stag-e are 

 Pseudomonotis sttbcircularis Gabb, Rhahdoceras rtcsselli 

 Hyatt, Halorites americanus Hyatt, Placites sp. nov., and 

 Arcestes sp. nov. 



This same association is characteristic of the Noric of the 

 Mediterranean region. 



From the data brought forward in this paper it becomes 

 clear that the stratigraphy of the Triassic system of 

 America is in perfect harmony with that of the typical 

 regions, and that the richness of its faunas will compare 

 favorably with that of any in the world. The writer now 

 has more than three hundred species of cephalopods from 

 the Trias of Western America. 



Descriptions of the Species. 

 Genus Meekoceras Hyatt. 



Type, Meekoceras gracilitatis White, Fossils of the Jura-Trias of South- 

 eastern Idaho, 1879, p. hi; and Contrib. to Pal. No. 5, 1880, p. 112, pi. 

 xxi, figs. 2, a-d. 



Form compressed, discoidal, involute or evolute, sides flattened; venter 

 narrow, either flattened or rounded, no keels or furrows; umbilicus narrow 

 or wide; body-chamber short. Surface nearly smooth, or ornamented with 

 radial lateral folds; no tubercles, spines, nor spiral ridges. Septa ceratitic, 

 with rounded entire saddles and serrated lobes. The external lobe is short, 

 and divided by a siphonal saddle; the two lateral lobes are longer and there 

 is an auxiliary series present in most forms, consisting of a single lobe (ser- 

 rated or goniatitlc), or of a series of denticulations, some of which may be 

 partly individualized into lobes. 



The internal septa consist of a divided antisiphonal lobe, flanked by a 

 single lateral, although in some species there may be internal auxiliaries. 



