606 THE JOURNAL OF GEOLOGY. 



says that the Halobiae are not confined to such distinct hori- 

 zons as Mojsisovics thought. The stratigraphic position of 

 these beds is the upper Noric, where Hyatt 1 placed them, while 

 recognizing their transition character from the number of species 

 common to them and to the Hosselkus limestone. 



A somewhat similar fauna was found by the writer at the 

 Rush creek mine, Rich Gulch, Plumas county, and in a similar 

 stratigraphic position. 



The Hosselkus limestojie 1, — The Hosselkus limestone has the 

 same distribution as the Swearinger slates, being found always 

 above them. There is a thickness of about 200 feet of these strata, 

 of a rather uniform character. The rocks are usually siliceous, 

 especially toward the top. Fossils are plentiful all through the 

 strata, but are easy to get out only at the base ; higher up the 

 rocks are so silicified that it is almost impossible to get fossils 

 out. 



The Hosselkus limestone may be conveniently divided into 

 three divisions, the lowest of which is the Trachyceras beds, so 

 called from the large number of that genus found at this horizon. 

 These beds are about 50 feet thick, and are composed of rather 

 hard pure limestone, made up almost entirely of fossils ; a large 

 majority of all the Triassic species were taken from this horizon. 

 The best collecting ground was found on the ridge between 

 Squaw creek and Pitt river, about, three miles northeast of Madi- 

 son's ranch. The following fossils were collected at this locality : 



Arpadites aff. A. cinensis, Mojsisovics. 

 Balatonites sp. group of B., Arietiformes. 



" " B., Gemmati. 



Polycyclus conf. henseli, Oppel. 

 Tirolites conf. foliaceus, Dittmar. 

 Trachyceras conf. aon, Muenster. 



" aff. aonides, Mojsisovics. 



" conf. archelaus, Laube. 



" aff. armatum? Muenster. 



" conf. ladinum, Mojsisovics ? 



" conf. hylactor, Dittmar. 



'Bull. Geol. Soc. Am., Vol. III. p. 390. 



