GEOLOGY OF THE ATTICA AND DEPEW QUADRANGLES 25 



concretions are common in the shale and blocky calcareous layers 

 2 to 5 inches thick occur at intervals of from I to 5 feet and a few 

 thin flags also appear at some outcrops. The passage from dark to 

 light shale at the bottom and from light to dark at the top is in 

 both cases gradual through several alternations in 5 to 10 feet, but 

 the formation presents an aspect so different from the beds above 

 and below as to make recognition easy. 



It was described and considered as the lowest member of the 

 Portage group by Prof. James Hall in the Report on the Geology 

 of the Fourth District, 1840, and by him designated the Cashaqua 

 shale on account of its specially fine exposure along Cashaqua creek 

 in Livingston county. The Cashaqua beds are 165 feet thick in the 

 Genesee River gorge and but 32 feet in the cliffs on the shore of 

 Lake Erie. 



Fossils are not found in great abundance in these beds, but are 

 fairly common in some of the upper shales, and some of the large 

 flat concretions in the upper part of the formation contain finely 

 preserved goniatites and orthoceratites. 



The following are the more common and characteristic species 

 of the Cashaqua shale : 



Manticoceras pattersoni Hall 



Probeloceras lutheri Clarke 



Tornoceras uniangulare (Conrad) 



Bactrites aciculum Hall 



Orthoceras pacator Hall 



O. Ontario Clarke 



O. filosum Clarke 



Phragmostoma natator Hall 



Lunulicardium (Pinnopsis) acutirostrum Hall 



L. (Pinnopsis) ornatum Hall 



Pterochaenia fragilis Hall 



P. cashaqua Clarke 



Honeoyea major Clarke 



Ontaria suborbicularis Hall 



O. accincta Clarke 



Buchiola retrostriata (von Buch) 



Paracardium doris Hall 



Paleoneilo petila Clarke 



Lingula ligea Hall 



Aulopora annectens Clarke 



Melocrinus clarkei Williams 



Exposures. There are good exposures of the Cashaqua beds 

 in both branches of Tannery brook a mile west of Attica. In the 

 Murder Creek ravine at Griswold the entire section may be seen to 

 excellent advantage. The upper beds are well shown below the 



