ONONDAGA REEF OF WILLIAMS VILLE, NEW YORK 341 



are also numerous, and generally more or less dissociated into their 

 component joints. In the center of this old quarry is a smaller sub- 

 sidiary reef composed of the same fossils, notably of Cystiphyllum. It 

 consists of an unstratified mass of cemented corals, mostly in the posi- 

 tion of growth, while the stratified beds dip away from it in all direc- 

 tions. The smaller reef, then, bears the same relation to the larger one 

 that the monticule of a volcano bears to the main cone. 



The corals of the bedded limestone in the neighborhood of the reef 

 are fragmental and may lie in almost any position. They indicate con- 

 siderable wave activity around the margins of the reef. Within the reef 

 brachiopods are less abundant than on its margin, while in quarries 

 opened at some distance from the reef brachiopods are abundant be- 

 tween the strata of fragmental limestone. As may be surmised, the 

 absence of bedding and jointage within the reef proper makes this por- 

 tion of the rock difficult to quarry, since it can be broken only by blast- 

 ing. Therefore we find that the reef is generally avoided in quarr3nng 

 operations, which is true even of the monticuloid subsidiary reef before 

 mentioned. 



SILURIC REEFS OF SOUTHEASTERN WISCONSIN* 



Reef structure is of common occurrence in the Siluric (Niagaran) lime- 

 stones of southeastern Wisconsin. One of the best known examples is 

 the old Shoonmaker quarry, near Wauwatosa. This has been fully de- 

 scribed by Chamberlin,t who recognized the reef character of the main 

 rock mass of the quarry. The quarry was opened in a mound or hill- 

 ock which undoubtedly owed its preservation to the hard character of 

 the reef mass. At the time of my visit, however, it had been abandoned 

 for a long time, and the tvalls had become more or less weathered and 

 overgrown, while the deeper portion was filled with water. The same 

 reef is exposed in the eastern part of the quarry, but there are smaller 

 reef-like mounds which may have been subsidiary reefs, or may be 

 merely parts of the larger one. No bedding is visible in the reef por- 

 tions, w^hich appear to consist mainly of stromatoporoids. These, how- 

 ever, are recognizable, as a rule, only on the weathered surfaces, the 

 general aspect of the fresh face being that of extreme massiveness of the 

 rock, with a total absence of stratification. Around the reef, however, 

 the rock is bedded and granular, and it may be seen in manj^ places 

 dipping away from the central reef portion. The highest dips which I 



* In the study of the reefs around Milwaukee I enjoyed the guidance and cooperation of Dr E. C. 

 Case, of the State Normal school, and in Cedarburg my studies were greatly aided by Mr Arthur 

 Roerner and the Reverend Charles Lange, of that town. To these friends my sincere thanks are 

 tendered. 



t Geology of Wisconsin, vol. ii, 1877, p. 364. 



