38 The Ohio Naturalist. [Vol. XIII, No. 2, 



2. Basal Bed; Red Clay Shales; Lowville. 

 The oldest Ordovician rocks, in that part of Lake Huron which 

 lies north of the eastern end of Manitoulin island, are exposed for a 

 distance of several miles along the western shore of Cloche penin- 

 sula, facing Cloche channel. At the northern end of the line of 

 exposure these oldest Ordovician rocks rest upon and against an 

 cast and west ridge of quartzite mapped by the Canadian Geolog- 

 ical Survey as Huronian. They consist of reddish clay shales 

 whose thickness is not known even approximately. At one local- 

 ity, along a small gully, a vertical section, 60 feet thick, is exposed 

 above lake level, whitish limestones making their appearance 70 

 feet above the lake, but the entire thickness of the red clay sec- 

 tion probably is much greater. Fossils were found at only one 

 horizon, at a locality about a mile south of the northwestern angle 

 of the peninsula, where a few feet of more or less indurated, 

 brownish, sandy layers are imbedded in the reddish clay section, 

 a short distance above the level of the new line of railway now in 

 the process of construction. Here a species of Ptcrolheca, closely 

 allied to Pt. atienuata but only about 20 mm. in width, and a 

 species of Cyrtodonta, 25 mm. long and closely related to C. janes- 

 villensis, suggest the Platteville or Low\dlle age of the strata 

 involved. Well preserved specimens of Archinacella and Lingula 

 also occur. 



3. Swift Current Beds; Chiefly Whitish and 

 Reddish Limestones; Leray. 



Along the southern half of Cloche peninsula, whitish limestones 

 overlie the red clays. Owing to the southward dip of the strata, 

 the base of this limestone series descends to water level more than 

 a mile before reaching Swift Current, the locality at which the 

 railroad passes from the peninsula over to Cloche island. The 

 general color of these limestones is whitish, but where they rest 

 upon the Huronian quartzites, and in the immediate vicinity of the 

 quartzite hills, they frequently are reddish. This reddish color 

 evidently is due to the material derived from the quartzites and 

 other Huronian strata which had been greatly disintegrated by 

 weathering before the deposition of both the basal red clays and 

 of the Swift Current limestones began. A quarry recently 

 opened at Swift Current, for the purpose of i)roviding the ballast 

 needed for the new line of railway, exposes JjcautifuUy the top of a 

 quartzite knoll covered by some of the upper layers of this lime- 

 stone section. Where these limestones are in contact with the 

 C[uartzite they not only are reddish in color but they also include 

 jjcIjI^Ics and smaller fragmental material, evidently derived 

 directly from the cjuartzite knoll. Among this fragmental 

 material occur most of the fossils so far collected, inckiding a 

 pygidium of Bath y urns, the sii)ho of Actinoceras bigsbyi, a Rhyii- 



