BIGSBY PALAEOZOIC ROCKS OF NEW YORK. 369 



expect to describe 200 species, exclusive of Corals and Bryozoa, of 

 which I already know fifty species." 



Fossils typical. — Until Mr. Hall's anticipations are realized, we 

 find in the Waterlirae group five typical fossils ; namely, 



Atrypa sulcata ; Orthis plicata ; Avicula rugosa ; Euomphalus sulcatus, 

 Littorina antiqua. 



Fossils occurrent in Europe. — Tentaculites ornatus (Mid- Silurian) ; 

 Spirifer plicatus ? ( Wenlock and Ludlow) ; Phragmoceras ventricosum 

 (Aymestry and Wenlock). 



Fossils recurrent in New York. — Spirifer plicatus; Terebratula hemi- 

 sphgerica ; Cornulites serpularius (all Wenlock) ; Leperditia alta. 



Lower Pentamertjs Limestone. 



Mineral Character. — This rock, according to De Verneuil (Bull. 

 S. G. Fr. iv. 656), in Central New York is distinguished by the 

 thickness of its strata and the compactness of its texture ; but ac- 

 cording to Mather, p. 347, the Pentamerus Limestone in his (the 

 south-eastern) district is divided into strata and slaty layers by seams 

 and thin partings of fine argillaceous slate or shale. It is in this 

 district a slaty and subcrystalline grey and black limestone. Its 

 upper layers contain here and there courses and flat nodules of horn- 

 stone. Vanuxem remarks that the divisional lines of its layers are 

 not straight (p. 118). 



Transition. — That this Pentamerus Limestone rests upon the 

 Waterlime group is all I can gather from authors. 



Place. — This is a very extensive set of strata in the south-east of 

 the State (Mather, p. 347), running continuously from the west line 

 of Schoharie County, eastward to the Helderberg Mountains in Berne 

 and Bethlehem, whence it extends south-east and south to Kingston, 

 and from thence south-west by Hurley to Rochester. 



It then disappears beneath the quaternary beds of the Mamakating 

 Valley, and is rarely seen from that place to Carpenter's Point on the 

 Delaware. It is conspicuous near the village of Schoharie. 



Taking up the description from Mather, Vanuxem (p. 118) says 

 that the Pentamerus Limestone enters Central New York (the region 

 allotted to him) from the south-east in considerable force, and con- 

 tinues to the Falls of Oneida Creek. Beyond this it is not distinctly 

 recognized. 



It does not exist from the west end of Madison County to Cayuga 

 Lake ; for from thence the Waterlime group, the Oriskany Sand- 

 stone, and the Onondaga Limestone come together, to the exclusion 

 of all the rocks intermediate to the Waterlime group and the Oriskany 

 Sandstone, which are found to the east. 



Position. — Conformable with and parallel to its associate strata. 



Thickness. — Vanuxem (p. 119) says that its maximum thickness is 

 in Otsego County, and is not less than 80 feet. It diminishes to- 

 ward the west, and little exceeds 10 feet on the Oneida Creek. Its 

 limit there is not so well defined as at the east of the State. In the 

 south-east of the State, at Schoharie, Mather (p. 347) found the 

 Pentamerus Limestone to be 12-20 feet thick. 



