I04 LOWER PENINSULA. 



annulated Orthoceras, resembling Orthoceras annulato-costatum 

 of Meek and Worthen. The specimens are thickly incrusted with 

 laminated strata of an amorphous limestone mass, which resemble 

 the incrustation by a Stromatopora, but have no trace of organic 

 structure. The siphon of the Orthoceras is central. An outcrop of 

 the underlying Waverly sandstone, two miles above Island Rapids, 

 has been previously described. The immediate contact of the 

 superimposed limestones with the sand rock is not seen ; the river 

 bed in the interval is formed by drift, and the slopes of the hillsides 

 bordering the river are all drift. Another locality where these 

 lower beds of the carboniferous limestone series can be observed 

 is on Cass River, 30 miles south of Caseville, in Town. 13, R. 1 1, Sect. 

 16. At the farm-house of Mr. W. H. Brown, situated close by 

 the river bed, the water flows in rapids over the oblique edges of 

 rock beds dipping at a moderate angle down stream. Here we 

 find a coarse-grained whitish sand rock with small punctiform, ferru- 

 ginous dots, and sometimes containing stems of Lepidodendron and 

 other vegetable remains. Interstratified with them are greenish, 

 micaceous sand-rock ledges and arenaceous, shaly seams. This sand 

 rock is the equivalent of the Point of Barques sandstone, and forms, 

 with few exceptions, the bed of Cass River for 6 or 8 miles up its 

 course to Indian Rapids, which were mentioned when I gave a de- 

 scription of the outcrops of the Waverly group. Only a few steps 

 below Mr. Brown's house, the sand-rock ledges are overlapped by 

 a bluish argillaceous limestone of a dull, earthy fracture and mod- 

 erately soft. It was from this rock that the Indians used to carve 

 their smoking-pipes. It contains numerous nodular concretions 

 of Zincblende, or Druse cavities filled with this mineral, or with 

 Brownspar and Dolomitspar. The Zincblende is mistaken by the 

 inhabitants for Galena, and the same mistake occurs on the old 

 maps of surveyors, lead ore being indicated as occurring in the 

 vicinity of Cass River. Stories are afloat according to which 

 Indians used to gather large quantities of lead on Cass River and 

 transform it at once into bullets, but I have little belief in such 

 accounts, especially since I have failed to find any thing to substan- 

 tiate them ; the only mineral observed by me was Zincblende. 

 This lime rock contains a moderate number of fossils, Produc- 

 tus, Spirifer Marionensis, Spiriferina spinosa, Syringopora ramu- 

 losa, and Orthoceras (annulato costatum ?), the same as those found 



