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* 4 



MUSEUM OF COMPARATIVE ZOOLOGY. 



317 



The subordinate ridgc-making members of the group are well shown in 

 the Quarry Hill synclinal ; they are the Lower Pentamerus, the upper 

 part of the Catskill Shaly, and the Upper Pentamerua ; while the Water- 

 lime, the junction of the Lower Pentamerus and Catskill Shaly, and of 

 the latter with the Encrinal, are marked by depressions. These relations 

 of hardness are pretty constantly shown in all parts of our field, and add 

 much to the ease of identification of the several subdivisions. 



The upper part of the Upper Pentamerus becomes sandy and impure 

 for about ten feet : this change is completed in the occurrence of a six- 

 inch layer containing limestone pebbles up to an inch in diameter, and 

 quartz grains of a quarter of an inch or less. Although no fossils were 

 found in this thin conglomerate, I have considered it as representing the 

 Oriskany sandstone, as it has the proper place in the series. Mather 

 and Emmons describe it as half a foot to two feet thick. The best ex- 

 posure of this layer was found on the north bank of the Catskill at 

 Leeds, in the vertical strata on the western side of the anticlinal that 

 shows there in the stream ; and again at several points below, as far 

 down a'B the railroad bridge. 



The Grits which come next are fine-grained, dark gray or bluish, and 

 generally with all appearance of bedding destroyed and supplanted by 

 an imperfect, nearly vertical cleavage. Bedding planes are sometimes 

 found, and generally contain impressions of the Spirophyton cauda-galli. 

 Very few other fossils were found in this monotonous formation. Its 

 thickness is three hundred and fifty feet, when measured by the breadth 

 of outcrop where the enclosing limestones were about vertical, east of the 

 limekiln near the junction of Old Kings and the Mountain roads. Other 

 observers give only a fifth of this thickness. Outcrops are generally 

 poor, as the rock usually weathers down to a rolling surface of gray 

 gravelly soil, or is covered by swamps; the lower half of the Grits is 

 more easily eroded tlsan the ujlpcr : the gorge of the Catskill by Leeds 

 pi-esents on its southern bank an excellent section of the entire forma- 

 tion (fig. 5), and exhibits perfectly the relation between its true bedding 

 and secondary fracturing. A small table-rock, over which a little stream 

 falls on its way to the Kaatcrskill west of West Eerg, an eighth of a 

 mile north of the limekiln above mentioned, shows many slabs near tlio 

 top of this formation well marked with the cocktail seaweed. 



The Corniferous limestone follows the Grits by an abrupt change ; its 

 layers are often massive, and always of a fine, close grain. Dark horn- 

 stone is very common in irregular masses often a foot broad ; it is clearly 

 of secondary origin. Fossils are scarce ; the corals so common farther 



