NIAGARA LIMESTONE. 367 



Ten paces of unexposed face succeeds, followed by 90 paces uncovered, which shows an 

 obscure dip of about 30 E. of S. Again 30 paces are concealed, bejond which a face 40 

 yards in length succeeds, whose dip is 33 E. of S. After another interruption of 60 

 paces, we find the last exposure of about 10 paces length, whose very obscure strati- 

 fication indicates a dip to the S. W. The ridge reaches a hight of about 45 feet above 

 the sole of the quarry. 



Near the summit of the ridge, at its western extremity, is a slight outcrop apparently 

 in place, and seeming to dip to the northwestward (20, N. 30 W.). If this be reliable, 

 we should infer that the ridge was comparatively narrow, as the exposure lies only 17 

 paces back from the face of the quarry. 



The trend of the ridge, as estimated from the exposures, is a little to the north of 

 east. 



The rock at Storey's and Schwickhart's quarries, within the triangle before 

 mentioned, is closely similar to that in the western part of Busack's quarry, and the 

 same remark may be made of the fossils, which consist mainly of Orthoceratites. 

 But in Busack's quarry, where the strata approach the reef, the fauna is much ampli- 

 fied, and we find Halt/sites catenulatus, an undetermined Trematopora, Streptelasma 

 and Fenestella, Stephanocrinus gemmiformis, Orthis biloba, 0. elegantula, Strophomeiia 

 rhomboidalis, Streporhynchus subplanum, Atrypa reticularis, Rhynchonella neglecta, 

 Platyceras Niagarense, Ortliocems annulatum, a new species of Phragmoceras, found 

 also in the adjoining reef, a Gomphoceras, Calymene Niagarensis, Encnnurus omatus, 

 and a new species found also at Zimmerman's quarry, Illcenus loxus, and Bronteus 

 Acamas. 



From all the foregoing facts, it may be regarded as fairly demonstrated that theso 

 horizontal beds were laid down simultaneously with the formation of the mounds. Tho 

 cellular nature of the rock of the latter, and the uncompressed condition of fragile fos- 

 sils, are fatal to any theory of upheaval, or other violent action. 



About five miles northwest of this, at Zimmerman's quarry, in Section 7, N. E. qr., 

 Wauwatosa, there is an even-bedded limestone of compact or minutely cellular texture, 

 very similar to that of some layers in the eastern part of Busack's quarry already de- 

 scribed, and to which they are equivalent, as shown by the contained fossils. As quar- 

 ried, the layers are thin, but the true beds are of more considerable thickness, a state- 

 ment which is true of most or all the flags and apparently thin-bedded strata of this 

 region. A few miles farther to the northwest, at Howard's quarry, and at several 

 other points in Menomonee, quarries of white and gray flags, and even-bedded, com- 

 pact, fine-grained, chertless limestones occur, that seem to belong to this horizon. At 

 Howard's are found Halysites calenulatus, Atrypa nodostriata, OrtJwceras annulatum, 

 0. medulare, Phragmoceras Nestor, Illcenus loxus, Calymene Niagarensis, and several 

 undetermined forms. At other points, fossils are rare. In the adjoining town of Lisbon, 

 as already mentioned, are similar strata, whose exact stratigraphical position is some- 

 what doubtful. From the fact that the compact, even-bedded rock that unquestionably 

 belongs to the Racine horizon is evervwhere, so far as known, free from chert, while 

 the strata immediately underlying the undoubted Racine beds at Waukesha are highly 

 cherty and the same is true of the layers beneath the Racine in all the northern- coun- 

 ties the presence or absence of chert is entitled to some consideration as a d istinguish- 

 ing feature. From its nature, however, I am disinclined to rigidly apply it as a diag- 

 nostic character, and, besides, such application would, in some cases, lead to strati- 

 graphical difficulties. It may be best, however, to provisionally regard the chertless 

 beds as belonging to the Racine horizon, and the cherty flags to the Waukesha beds. 

 If this rule be followed, most of the rock exposed in the town of Lisbon, and a portion 

 of that in Pewaukee, would bo regarded as Racine. In justification of the fact that any 

 doubt remains, it is to be remarked that this is a region of almost universally prevalent 



