318 



Report of the State Geologist. 



The thin layer beneath the "Styliola band " is blue and contains Hamil- 

 ton fossils, but is more fissile than the shale below, which contain trilobites. 

 Mr. A. W. Grabau, who has made a very careful study of this layer, says, it 

 appears to have the fauna of both the Moscow and Genesee beds, and may be 

 regarded as a passage formation from one to the other. 



The relation of the Encrinal limestone to the Styliola band and 

 associated rocks at Eighteen Mile creek is well shown in accompanying 

 photograph. 



Owing to its position near the upper part of the group and the ease with 

 which it can be traced, I have selected the Encrinal limestone as the horizon 

 of reference from which the top of the Hamilton and Genesee may readily be 

 found. It is easily recognized as a hard limestone, two feet or more thick, 

 usually stained on the under surface with iron rust from the decomposition of 

 pyi'ites, and containing large crinoid stems, some of which are nearly an inch 

 in diameter. Excepting a few outcrops of the " Basal limestone, 11 there is no 

 other rock in Erie county from the Stafford limestone up to the Portage sand- 

 stones sufficiently durable for bridge or building purposes. The shales 

 immediately above and for several feet below are always rich in fossils, among 

 which cyathophylloid corals and brachiopods, Atrypa reticularis, A. aspera, 

 Aihyris spwiferoides, Spirifer medial)'* and S. mucronatus, are particularly 

 abundant. Since it resists the action of water and other erosive influences 

 better than shales, it is found in almost every gully and ravine which cross 

 the outcrop. Along the lake shore westward from Eighteen Mile creek, it 

 forms a conspicuous band in the face of the cliff, dipping beneath the surface 

 of the water near Pike creek. The Styliola band may be seen above it, the 

 two limestones approaching each other slightly near the western limit. East 

 of Eighteen Mile creek, the Encrinal limestone caps the bluff for a short dis- 

 tance, and is next seen by the road near the house of Mr. Crocker, about two 

 miles further on, reappearing again in the face of the bluff beyond. From 

 here it can be easily traced to Wanakah, crossing the creek near the station 

 just below the railroad bridge. At Hamburg-on-the-lake it is a half-mile, and 

 at Athol springs about 200 yards east of the railroad. At Big Tree, it is 

 exposed in the railroad cutting near Hush creek, and on the banks of the 

 stream by the farmhouse above. At Windom, it is found for some distance 

 along the sides of the ravine, being well exposed just above the bridge near 

 tlif station and crossing the bed of the brook a quarter of a mile further up. 

 It is here about thirty inches thick, in two layers, the lower of which is the 

 thicker, and has three <>r four inches of pyrites at the bottom. The Styliola 



1 



