344 New York State Museum 



the dolomitic phase in Erie county, known locally as the 

 "Bullhead" limestone, the name Akron dolomite (Sherzer 

 and Grabau '09) has been given from the occurence at the 

 village of Akron. The Akron dolomite is a little later 

 faunal development than the Cobleskill (Hartnagel). 

 Among the characteristic fossils of the Cobleskill are the 

 corals Halysites cdtcnulatus, Favosites niagarensis, Diplo- 

 phyllum coralliferum and the cup coral Enterolasma cali- 

 culum, and species of Stromatoporas (hydrocorallines). 

 The coral Cyathophyllum hydraulicum and the brachio- 

 pod Spirifer eriensis are the characteristic fossils of the 

 Akron phase. In the Schoharie area and westward the 

 pelecypod Ilionia sinuata is characteristic and the pres- 

 ence of the trilobite Lichas (Corydocephalus) ptyonurus 

 always identifies the Cobleskill. 



The Rondout waterlime (Clarke and Schuchert '99) 

 received its name from the fine development in the ex- 

 tensive quarries and cement mines in the vicinity of Ron- 

 dout. The same beds have also furnished cement in the 

 Schoharie area. This drab-colored waterlime, formerly 

 known as the "Salina waterlime," extends as far west 

 as Seneca county where it is overlapped by the Onon- 

 daga. In the intervening area it lies between the Cobleskill 

 and the Manlius. The average maximum thickness is 

 40 feet, but in the Cobleskill region it thickens to 60 feet, 

 the lower six feet of which are mined for cement in 

 Howe's Cave. In certain areas (as Rondout) the sur- 

 face of some beds is characterized by mud crack struc- 

 tures, mostly of pentagonal form, indicating exposure of 

 the lime mud at times to the drying influence of the sun. 

 The coral Favosites helderbergiae var. precedens has 



