316 BULLETIN OF THE 



feet on the eastern slope of the Quarry Hill. The best exposure is on 

 the Catskill on the first bend above Austin's Mill, where broad surfaces 

 of the limestone are laid bare ; it is fairly shown in the ridges or bluffs 

 all along its outcrop. 



The Catskill (formerly Delthyris) shaly limestone is a rather evenly 

 bedded, thin splitting, impure dull blue rock weathering gray or brown 

 as its calcareous particles disappear. Fossils are very common, but on 

 weathered outcrops are found only as casts : the ordinary forms are 

 Spirifer macropleura, Spiriferina perlamellosa, Streptorhynchus {Hemi- 

 pronites) radiatus, Strophomena rhomhoidalis, Rhynchonella vetitricosa, 

 Eatonia peculiaris, and Pterinea communis* The thickness of this 

 division is somewhat under one hundred feet. The best exposure is at 

 the railroad bridge across the Catskill, three quarters of a mile below 

 Leeds, and on the banks farther down stream ; but characteristic fossils 

 are easily found at many points. 



The Encrinal and Upper Pentamerus limestones were not separated 

 in our study, as they constituted a single topographic element ; but it 

 was readily seen that crinoid stems were more plentiful in the lower than 

 in the upper layers. The rock is hard, heavy-bedded, and coarse-grained, 

 consisting of broken shells and crinoid stems ; it is well adapted to 

 heavy masonry ; on some weathered joints, exposed in French's Quarry, 

 very clear cross-bedding was seen. Corals make no important share of 

 these limestones so far as we could discover. The shells recognized were 

 Pentamerus pseudo-galeatus, Spirifer cycloptera, and many others not de- 

 termined : they are so firmly held, that it is difficult to break out good 

 specimens. The thickness of these two members as determined at the 

 railroad bridge below Leeds is one hundred and twenty feet, but this 

 may be exaggerated by local faulting. Other observers give it much 

 less. French's Quarry and the Catskill bank by the railroad bridge give 

 good exposures ; and fair outcrops are found at many other points. 



These Lower Helderberg limestones as a whole are decidedly harder 

 than the shaly sandstones below or the grits above them, and are strongly 

 determinant in forming ridges and bluffs. Among the most marked of 

 these is the long, continuous ridge at their easternmost outcrop, known 

 as the Kalk Berg (corrupted into Kalla Barrack f), where they are usu- 

 ally nearly vertical and sometimes are overthrown : other interesting 

 forms of outcrop appear on the several synclinal and anticlinal folds. 



* The names are thus given in the collection in the American Museum of Natural 

 History, New York. 



t For these local names I am indebted to Mr. Henry Brace of Catskill. 



