374 J. S. DILLEE — GEOLOGY OF THE TAYLORVILLE REGION. 



the collection. Professor Fontaine, who studied the collection, reports 

 that it contains Equisetum mumteri, Podozamites or Pterophyllum, and three 

 small ferns, besides Acustichides princeps and Lagenopteris or Cheiropteris. 

 According to this paleontologist, in whose report the plants are described 

 in some detail, " They are clearly Mesozoic and most probably Rhsetic in 

 age. * 



The Hosselkus limestone is well exposed where burned for lime and 

 near the Cosmopolitan mine, on the divide between Genesee valley and 

 Hosselkus creek. It contains numerous remains of the genus Arcestes, 

 with a few other fossils, besides abundant pentagonal crinoid stems. 

 Although there are some round crinoid stems present, the preponder- 

 ance of pentagonal ones, in connection with. Arcestes, furnishes a ready 

 means of distinguishing this upper Triassic limestone from those of 

 Jurassic, Silurian or Carboniferous age. It is one of the most important 

 formations of the Taylorville region, and has been recognized elsewhere 

 at numerous outcrops between Spanish ranch and Prattville and at many 

 other points far to the northwestward, even beyond Pit river, in the 

 Klamath mountains. t 



The Swearinger slates are dark and calcareous, with a thin blue lime- 

 stone and some siliceous layers. They occur just above Swearinger's 

 house, on the northern side of Genesee valley, and include the Monotis 

 bed. Rhabdoceras limestone and Halobia slates of Hyatt. They are all 

 upper Triassic and rest directly and unconformably upon the Carbon- 

 iferous. 



The Trail beds, which lie farther northeastward, have not furnished 

 a sufficient number of characteristic fossils to determine their age. On 

 structural grounds, however, they also are regarded as Triassic, and 

 probably newer than the Hosselkus limestone. 



The Robinson beds contain slates, conglomerate, tuff" and sandstone, 

 of which the last two are the most important. The sandstone is a pur- 

 plish rock of great variability. One-fourth of a mile south 50° west of 

 Robinson's, in Genesee valley, it becomes for a short distance an arena- 

 ceous limestone. This calcareous portion was discovered by Curtice and 

 has yielded an abundance of Carboniferous fossils. The material of which 

 it is composed is chiefly volcanic, and close by the locality just men- 

 tioned it passes into a well marked tuff. The latter sometimes to the 

 naked eye closely resembles the porphyritic eruptive with which it is 



♦ Letter of December 8, 1891. 



j-The name Klamath mountains was first used by Powell (lecture before 1 1 1 < - National Geographic 

 Society, February 17, 1888, not published) to designate the topographic province in northwestern 

 California and southwestern < iregon in which the Sierra Nevada, ' lascade and < loast ranges meet. It 

 embraces tie' mountains locally known near the coast, between the 40th and 4 It li parallels, as Yallo 

 Bailey, Bully Choop, Pil River, Mail.].'. Trinity, South Fork, Scott, Eddy, Salmon, Siskiyou. Rogue 

 River, Umpqua and Calapooya mountains. 



