296 GEOLOGY OF EASTERN WISCONSIN. 



whole a Hglit, yellowisli buff aspect. The gray portions are more 

 compact and crystaUine than the buff, which are porous and earthy 

 although beautifully bespangled with glistening crystalline facets. 

 These characters apply more particularly to the lowest and uppermost 

 members; the latter is distinguished by the presence of nodules of 

 chert. A portion of the intermediate layers, while retaining some- 

 thing of the nature above described, becomes much more irregular in 

 texture, and possesses a very rough fracture, which gives the ledges 

 in the quarry a brecciated appearance that is increased by the pres- 

 ence of cavities. 



Another portion is more homogeneous in structure than either of 

 the preceding kinds, and has a very noticeable conchoidal fracture, 

 resembling in this respect the glass rock of the Lead region, from 

 which, however, it differs in having a less compact and more earthy 

 texture, caused by the presence of from 12 to 15 per cent, of alumin- 

 ous and silicious material. It is lined with obscure reddish stains, 

 probably of fucoidal origin. This constitutes two bands, two to four 

 feet thick, lying near the center of the division and separated seven 

 or eight feet from each other. They thus constitute reliable laud- 

 marks in correlating partial exposures at distant points, and, if intel- 

 ligently used, will prove a serviceable guide to the quarryman. 



The life at this stage was, as has been remarked, very similar to 

 that at the time of the deposit of the Lower Buff beds, but was more 

 prolific and varied. Nearly sixty species are known to occur in these 

 beds, and it is presumable that the actual number is much larger. 



Of these, between fifteen and twenty have not been found in the 

 Lower Biiff beds, but until more thorough search has been made it 

 would not be wise to regard them as diagnostic. The occurrence of 

 ■Halysites at this horizon is especially worthy of remark, as being the 

 lowest point at which it has yet been authentically reported in the 

 western series. 



4-. The Upper Blue Beds. These are so similar in general charac- 

 ter to the Lower Blue Beds, as not to need extended description. 

 They differ from them chiefly in those cases where they take on a 

 coarse granular character, approaching that of the Galena limestone 

 above, to which they constitute the transition. The degree in which 

 they are thus modified varies with the locality. At several points 

 there are only four or five such transitional beds, and at other points 

 the whole division shows something of this character. 



An abundance of Brachiopods, Bryozoans and Chwtetoid corals 

 form the leading feature of the life of this period. Its general aspect 

 is more manifestly similar to that of the Cincinnati shales above the 



