120 NEW YORK STATE MUSEUM 



is the lagoon region between the barrier reef and the shore "which was not 

 far to the east." Its fauna is greatly different from that of the reef, the 

 heavy Nerineas and Diceras and the corals having entirely disappeared. 



On the other side of the reef the corals disappear suddenly and the 

 pelagic facies extends far toward the north into the open sea. It is charac- 

 terized by Ammonites, Belemnites, brachiopods and Echini. 



The great numeric preponderance of the cephalopods in the lower 

 Shelby dolomite would, by comparison with the equal preponderance of this 

 class in the pelagic facies of the reef, suggest that this may represent the 

 pelagic facies or pelagic side of an early Guelph reef. 



An excellent description of the facies of the ancient coraliferous sea 

 of Racine age in Wisconsin has been given by T. C. Chamberlin. 1 We 

 quote part of his interesting summation : 



It appears, then, that in the southern counties there are three well 

 marked classes of limestones, with intermediate gradations, one class, con- 

 sisting of very irregular often brecciated or conglomeritic dolomite, forming 

 masses that usually appear as mounds, or ridges of rock, of obscure stratifi- 

 cation, a second class, formed of pure, soft, granular dolomites, a part of 

 them calcareous sandrock, and a third class, consisting of compact, fine 

 grained, regular, even beds. We have demonstrated that the three forms 

 change into each other when traced horizontally. They were therefore 

 formed simultaneously. The view that best explains these facts is, (i) that 

 the mounds and ridges were ancient reefs, and (2) that the granular sand 

 rock was formed from calcareous sands, derived by wave-action from the reef, 

 and (3) that the compact strata originated from the deposit of the finer cal- 

 careous mud that settled in deeper and more quiet waters, the whole process 

 being analogous to, if not identical with, the coral formation of the present 

 seas. 



But before pursuing this analogy farther, it will be well to consider the 

 evidences of life found in these rocks. While some of the reefs, or at least 

 that portion of them that happens to be exposed to examination, present 

 only a few fragments of fossils, others are prolific in organic remains, and 

 some of them are remarkable for the richness and variety of their fauna. 

 The reef near Wauwatosa (Schoonmaker's quarry), is a striking instance of 

 this. There have been collected from it, chiefly by Dr Day, probably not 

 less than 200 species. Of these there have been identified 28 corals, 8 bryo- 



* Geol. Wisconsin. 1877. 2:368-71. 



