156 E. D. McEwan — Ordovician of Indiana. 



lower part of the division is located along the creek and 

 the upper part is in the gully heading just north of the 

 south cut. 



CORRYVILLE-MOUXT AUBURX . 



Corryville species continue until the end of Maysville 

 time. The introduction of Platystropliia ponderosa 

 auburnensis (Foerste), and Coeloclema oweni (James) in 

 the beds 77 to 83 feet above the lowest exposure indicates 

 the advent of Mount Auburn time. The lumpy layers 

 of limestone in which some of the Corryville-Mount 

 Auburn faunal list occurs suggest that the close of Mays- 

 ville time was marked by shallow water. No definite 

 evidence of a disconformity was observed. It may be 

 that the sea never entirely retreated from the area. 

 The presence of several Maysville species associated with 

 Arnheim species supports this. However, the faunal 

 aspect as a whole underwent great change, and it is 

 likely that over most of the interior the end of the Mays- 

 ville and the advent of Richmond time is marked by a 

 general retreat and advance of the sea. 



Arnheim 



The Arnheim is marked by the disappearance of most 

 of the Maysville species and the invasion of large numbers 

 of Richmond species, such as Homotrypa pulchra (Bas- 

 sler), Batostoma varians (James), Mesotrypa orbiculata 

 (Cumings and Galloway), Peronopora decipiens (Rom- 

 inger), Platystropliia foevstei (McEwan), and P. ivallo- 

 ivayi (Foerste). The division is found in the upper 

 part of the gully and the lower part of the cut along the 

 railroad. 



Waynesville. 



The upper 83 feet of this section show a definite in- 

 vasion of great numbers of Waynesville species, such as 

 Amplexopora pustulosa (Ulrich and Bassler), Hetero- 

 trypa subramosa (Ulrich), Homotrypa flabellaris 

 (Ulrich), H. wortheni (James), Homotrypella liospitalis 

 (Nicholson), Stigmatella crenulata (Ulrich and Bassler), 

 Bythopora meeki (James), Dolman ell a meehi (Miller), 

 Atactoporella schucherti (Ulrich), E ridotrypa simulatrix, 

 Platystropliia annieana (Foerste), P. cyplia var. Cata- 

 zyga headi schuchertana (Ulrich), and Strophomena 

 planumbona (Hall). 



