WACHSMUTH ON CRIXOID REMAINS. 420 



was round also in the proximal part, as the form of the stem changes greatly in its 

 downward course, and it seems to me the upper face of the root shows traces of that 

 petaloid structure to which I alluded. The other specimens show the same thing 

 as number 4, but less distinctly. The genus Pentacrinus, winch made its appear- 

 ance in the Jurassic, survived to our present day ; and as the structure of the stem 

 remained almost unchanged, it is difficult to refer your specimen to any definite 

 age, but I am quite certain they are not older than Jurassic." * * * 



Mesozoic Conglomerate containing older line];*. — The fossiliferous lime- 

 stones alternating with slates and greenstones are atone point associated 

 with a conglomerate containing pebbles and bowlders of granite and 

 quartzite. The locality is on Rush creek, a little less than a mile in a 

 straight line from its confluence with the East branch of the North fork 

 of the Feather, in the northern part of section 8, T. 25 N., R. 8 E. The 

 conglomerate is in contact with the limestone, and its cement is limy- 

 The granite of the pebbles and bowlders is like that of Spanish peak 

 mountain, and the quartzite like the pre-Mesozoic quartzites of the easterly 

 and northeasterly faces of that mountain, and there is no other probable 

 source of these bowlders and pel titles than within this westerly area of 

 uplifting. It is plain, therefore, that the granite- had cooled and crys- 

 tallized, ami the slates had been deposited and had undergone quartzitic 

 alteration and been raised above sea-level and subjected to subaerial 

 erosion, before these conglomerates were deposited on the beach of the 

 arm of the Mesozoic sea. These rocks are therefore unconformable with 

 the pre-Mesozoic strata, although no unconformity of dip and strike is 

 apparent, I saw one granite pebble or bowlder of more than 500 cubic 

 inches in size in the conglomerate. 



The conglomerate is on the easterly edge of the limestones and limy 

 slates, which are exposed for a. widtli there of 5,300 feet and a thickness 

 of about 4,600 feet. On the west of them and between them and the pre- 

 Mesozoic rocks is the broad belt of serpentine three miles wide. I found 

 no fragments of serpentine in the conglomerate. The serpentine, being 

 an eruptive rock, may have keen deposited on land or in water, hut the 

 slates ami limestones were certainly deposited in the sea. If these and 

 the serpentines had been deposited when the pebbles of this conglom- 

 i rale were borne to the beach, they must have come across a width of some 

 miles of water, unless the serpentines and slates had been uplifted. Of 

 tins there is no evidence ; and as it is not possible that this beach material 

 came across an arm of the sea (one pebble of granite containing more 

 than 500 cubic inches'), H follows that the conglomerate and the green- 

 stones to the east of it are older than the slates and limestones ami ser- 

 pentines to the west of it. It is true that the serpentines now come in 

 contact with the pre-Mesozoic rocks al the faulted easterly face of Spanish 



I.I \ I : i i i < ■ i . i 9<>i Vm., Voi,. 3 18(11. 



