30 



It is about three inches thick, and in most places consists 

 entirely of an accuninlation ofcyathophylloid or cup corals. 

 These are mostly ot the genera HeliophyUuin [H. hnlli E. & 

 H.) Cvstiphyllum and Zaphrentis, and nearly all lie pros- 

 trate. Frequently three or lour lie above each other, as if 

 the}^ had been carried in by a strong flood and spread over 

 the sea bottom. They show, however, no signs of wear, the 

 delicate bryozoans and small corals which encrust many of 

 them, showing that little, if any distiu-bance has occurred 

 here since the growth of the corals. They therefore indicate 

 a flourishing coral reef or forest, which was suddenly over- 

 whelmed, probably by the influx of mudd^" \vaters, and was 

 completely destroyed, without, however, undergoing any 

 mechanical abrasion. The appearance of these large corals 

 seems to have driven out the small Streptelnsma, for this 

 coral, adapted probably to muddy waters, occurs above and 

 below the coral layer, but not in it. 



Associated \vith the corals, and becoming the sole occu- 

 pants of the bed in the absence of the corals, are a number of 

 brachiopods, usually^ of robust character. These are Spiriier 

 audaculus var. eatoni ( Hall), Atrvpa reticularis { Linn. ) and 

 .4. aspera (Dalman). The latter form is restricted to this 

 bed, and is abundant in all its outcrops. A curious feature, 

 however, is, that nearh' every specimen has lost its spines, 

 while the same species in the Genesee ValW, where it is 

 associated with the same species of corals, nearly always 

 retains its spines. That the loss of the spines in this region 

 is due to protracted maceration before final burial seems 

 likely, and would be in direct accord with the slight thick- 

 ness of the Moscow shales in this region.* 



The Encrinal Limestone. This rock appears for the first 

 time near the iipper end of Section 5, where it causes the fall 

 in the stream. Above this point it quickly dips below the 

 Moscow shales, and is not seen in any of the upper sections. 



•See Chapter III. 



