DEVONIAN AGE. 



255 



In contrast with the above, the rock of the Corniferous epoch is one 

 .of the great limestones of the continent. The layers of limestone 



Spirophyton Cauda-galli. 



sometimes contain seams of hornstone (flint-like quartz); and to this 

 the name Corniferous alludes, from the Latin cornu, horn, and fero, 

 I bear. Much of it abounds in corals, as much so as the reef-rock of 

 modern coral seas. The formation extends from east to west through 

 New York, and is continued westward through Canada and much of 

 the great Interior basin, having fully as wide a range as the Niagara 

 limestone. It exhibits its coral-reef character grandly at the Falls of 

 the Ohio, near Louisville, where corals are crowded together in great 

 numbers, some standing* as they grew, others lying in fragments, as 

 they were broken and heaped up by the waves, branching forms of 

 large and small size mingled with massive kinds, of hemispherical and 

 other shapes. Some of the cup corals (Cyathophylloids) are six or 

 seven inches across at top, indicating a coral animal seven or eight 

 inches in diameter. Hemispherical compound corals occur five or six 

 feet in diameter. The various Coral-polyps of the era had, beyond 

 doubt, bright and varied coloring, like those of our own tropics ; and 

 the reefs were therefore an almost interminable flower-garden. 



A limestone made up of similar corals occurs on Lake Memphrema- 

 gog, between Vermont and Canada, showing that coral reefs flourished 

 there also ; and other localities exist to the eastward. At Cape 

 Gaspe on the St. Lawrence Gulf, over the Gaspe limestones, there are 

 7,036 feet of sandstones, a portion of which, in the lower part, are sup- 

 posed to be of the Corniferous period. 



The formation in New York consists of two members, the Onondaga limestone or 

 lower part, and the Corniferous limestone or upper. The hornstone occurs in the latter. 

 This hornstone contains various microscopic fossils (Fig. 484 A), and also minute 

 rhombic crystals, l-500th inch across, which are probably calcite. The thickness of 

 .the two limestones in New York is in some places 350 feet. 



