NIAGARA FALLS AND VICINITY 135 



This coralline is generally very massive and may attain a diameter 

 of 2 feet. Probably includes a number of distinct species. 



£ 



Fig. 2S Stromatopora concentrica Hall with an enlargement of a cross-section 



Found at Xiagara in the Lockport limestone, particularly the 

 geodiferous beds, and generally common throughout the middle 

 limestones. Also at Lockport and elsewhere. 



Class ANTHOZOA Ehrenberg 



The Anthozoa, or coral polyps, are marine animals ranging from 

 low water to 300 and sometimes even 1500 fathoms (Zittel). The 

 reef-building types however do not flourish in depths greater than 

 50 fathoms, and are generally restricted to 20 fathoms or less. 

 Both simple and colonial forms occur, the latter predominating at 

 the present time, while the former were abundant in the Paleozoic. 

 The two important types of Paleozoic corals are the "rugose corals" 

 or Tetracoralla, and the tabulate corals, the former generally simple, 

 the latter colonial types. 1 



The simple rugose corallum is well represented by Entero- 

 lasma. It consists of numerous radiating septa, disposed in 

 several cycles, and united round their outer margins by a wall or 

 theca (pscudotheca). This is formed by the lateral expansion or 

 thickening of the septa in that region. The exothecal prolongations 

 of the septa are visible on the exterior of the corrallum as costae, 

 which are frequently represented by grooves instead of ridges. 

 These, in the genus referred to, as well as in others, commonly 

 show the peculiar tetrameral arrangement characteristic of the septa 

 of this group. On or near the convex longitudinal surface of the 

 corallum a median, or " cardinal ", septum appears, from which the 



*As no true Hexacoralla occur in the formations treated of in these 

 pages, an account of their structure is omitted. 



