426 PRINCIPLES OF STRATIGRAPHY 



Eridophyllum, Synaptophyllum and Diplopliyllum occur here, their 

 interstices filled in with coral sands. Favosites likewise ahound, 

 the heads being often of enormous size. Large Cystiphyllums and 

 Cyathophyllums also occur, and crinoid stems are equally abundant. 

 In the bedded limestones near the reef, fragments of Favosites 

 abound, and sometimes heads of great size occur, but they are 

 partly worn, and very commonly overturned. Here we have the 

 coral breccia formed of the dead coral heads on the borders of the 

 reef, enclosed in the coral sand derived from the reef by the grind- 

 ing action of the waves which rolled about these fragments of 

 coral and used them as tools for their destructive work. Brachio- 

 pods, bryozoans, molluscs and other lime-secreting organisms are 

 also plentiful on the borders of the reef, while the remains of giant 

 placoderm fishes found in these deposits further complete the 



^^S- -.-^--^.^^^.^^S^w^.^^ 



f^^^*^''> - \' ^ i-O.l- JC-t^' -r-,-- , ^^,' ■ 



lx£_v ^-r- ■ t V f 



Fig. 87. Section of a reef in the Onondaga limestone of Williamsville, N. Y. 

 Two quarries have been opened in this section, one on either side 

 of the reef. The left-hand (eastern) quarry does not quite touch 

 the reef, but the floor of the right-hand (western) quarry rests 

 partly upon the reef and exposes the low secondary reef-mound. 



faunal list and show us some of the organic agents influential in the 

 destruction of the coral reef and the production of the coral sand. 

 These fishes are especially abundant in the later deposits of this 

 series in Ohio and Michigan, from which 19 species have been 

 obtained as against 8 species from the Onondaga of New York. 



In some portions of the Ohio limestones small globular bodies, 

 CalcispJiccra robitsta, abound, sometimes making up the liinestone. 

 These resemble the spore capsules of the fresh-water lime-secreting 

 alga, Chara, and may be part of a plant, or more probably a foram- 

 iniferan, of the kind living abundantly to-day in the quiet waters 

 of the lagoons within the coral reefs. (See description of Funa- 

 futi.) 



Reefs of this age are likewise found in southern Indiana and 

 adjacent portions of Kentucky ( Jeffersonville limestone of the 

 Falls of the Ohio). 



Middle Devonic Reefs of Miehigaii. In the Hamilton or Trav- 

 erse group of Michigan reefs are well developed, and almost every 



