TJie Corals of Delafield. 185 



THE COEALS OF DELAFIELD. 



By Ira M. Buel. 



The large collection of fossils made by the Geological Survey 

 at Eoberts' quarry, Delafield, Wisconsin, is surpassed in interest 

 and scientific value by no other representation of Palaeozoic 

 fauna ever obtained from our state. It contains thousands of 

 specimens almost perfectly preserved by the blue friable shale in 

 •which they were imbedded ; and of the seventy species already 

 distingiiished, about one-half are new to science. The coralline 

 representatives found here are of special interest to the student 

 and naturalist. 



The locality in question (Sec. 21, T. T, R 18 W.) lies on the 

 southern shore of Pewaukee lake, and in the edge of a trough 

 carved by glacial forces out of the lower layers of the Niagara 

 limestone, and the soft underlying Cincinnati shales ; the basin 

 being occupied in part by the lake itself. By the removal of the 

 limestone layers in the quarry, quite a surface of this shale was 

 exposed, and as this formation somewhat resembles some of the 

 Carboniferous shales, it was supposed by some inquiring mind to 

 belong to that formation. A shaft was accordingly sunk at this 

 point for the discovery of coal, and was not abandoned until a 

 depth of fifty feet had been reached. The mound of rock and 

 clay thrown out of this pit or shaft, the rain-washed monument of 

 a geological delusion, was the source of all of the specimens ob- 

 tained from that locality. 



These corralline forms are all of small size, the smallest species 

 measuring about an inch in length and about a tenth of an inch 

 in diameter. The largest coral fragment is about two inches in 

 diameter and consists of a sort of central base from which a num- 

 ber of slender arms branched out. Within these limits we find 

 almost every possible variation in form, manner of growth, branch- 

 ing and surface markings. 



The size, form and arrangement of cells and cell walls, are the 

 principal distinguishing features of these corals ; and as these feat- 

 ures are mainly microscopic, the labor of identification of species 

 and varieties among these thousands of specimens was not a small 



