270 PALEOZOIC TIME — DEVONIAN AGE. 



formation has been recognized in Ohio, along the shores of Lake Erie, in Michi- 

 gan, Indiana, Illinois, Kentucky, Wisconsin, Iowa, Missouri, and other parts 

 of the Mississippi basin, but the subdivisions above mentioned are not distin- 

 guishable. In the Michigan peninsula the thickness is 354 feet (Winchell) ; in 

 Iowa, 50 to 60 feet (Hall); in Missouri, from a few feet to 75. The rocks are 

 finely displayed at the Falls of the Ohio, near Louisville, Ky., and are as full 

 of fossil corals as any modern coral reef. 



The upper layers of the rock in New York, which are usually dark grayish, 

 are nearly black on the Niagara. In some localities west of New York the rock 

 is oolitic. In Missouri, siliceous and sandstone layers alternate with the lime- 

 stone. The hornstone of the Corniferous beds is often left in rough projecting 

 masses where the limestone portion has been worn away by the action of 

 water. These rocks outcrop also in southwestern Canada, N. of Lake Erie. 



(b.) Appalachian region. — The Upper Helderberg formation has not been ob- 

 served among the rocks of Pennsylvania except northwest of the Kittatinny 

 Mountain, between the Delaware and Lehigh Rivers. 



(c.) Eastern border region. — At Owl's Head, on Lake Memphremagog, near the 

 northern borders of Vermont, there is a true coral-reef rock, full of corals, over- 

 laid by talcose schist ; and, although partially metamorphic, many of the speci- 

 mens of fossils are tolerably perfect. Among the species, Billings has recog- 

 nized Syringopora Hisingeri B., Favosites basaltica Goldfuss, Biphyphyllum 

 8tramineum B., and Zaphrentis gigantea Lesueur. Besides these, according to 

 Hitchcock, Atrypa reticularis has been identified by Hall. To the south, in 

 Massachusetts, at Bernardston (west of the Connecticut, and not far from 

 Greenfield), there is also a metamorphic limestone of this epoch, with fossils (C. 

 H. Hitchcock). It is altogether probable that Devonian beds stretch south from 

 Lake Memphremagog j for the rocks have this strike through the whole length 

 of the State (and through New England generally); and the limestone may be 

 represented among them, — perhaps in the Calciferous mica schist, which Hunt 

 has suggested may be a metamorphic limestone. It is also supposed that the 

 Upper Helderberg limestone occurs south of the St. Lawrence, between Vermont 

 and Gaspe. 



II. Life. 



1. Plants. 



The plants thus far observed are sea-weeds and Protophytes. No 

 land-plants of the period are known. Fig. 441 represents the 

 " Cauda-Galli" sea-weed characteristic of the first epoch. 



The protophytes occur in the hornstone of the Corniferous lime- 

 stone, and appear to be very abundant throughout it. The dis- 

 coveries were made, but a few days before these pages were printed, 

 by Dr. M. C. White, of New Haven. Through his investigations, 

 and others, since made, by F. H. Bradley, it is now known that 

 organisms similar to those figured below (fig. 441 A) are common 

 to the hornstone of both older and later Palaeozoic periods. The 



