Handbook of Paleontology 407 



eluded in the Portage beds have now been put under the 

 Chemung (Chad wick '19). The Chemung group here 

 begins with the Dunkirk black shale (Clarke '03 ; Luther), 

 named from Dunkirk in Chautauqua county. The for- 

 mation has a thickness of 50 to 100 feet. The sandstones 

 in this black shale increase until east of the Genesee val- 

 ley very little black shale remains in the lower 150 feet 

 of arenaceous beds with full Chemung fauna, and these 

 beds are called the Canaseraga sandstone (from Cana- 

 seraga; Chadwick T9). These sandstones include the 

 layer termed Longbeards Riffs sandstone (Clarke '03; 

 Luther), named from the riffs on the Genesee river in 

 Allegany county, eight miles south of Portageville. The 

 Dunkirk-Canaseraga beds are believed to correspond to 

 the basal Cayuta shale in the Ithaca region. The Go- 

 wanda beds (for Portage preoccupied of Luther '03j 

 named from Go wanda (Lodi), Cattaraugus county 

 (Chadwick '19) everywhere directly overlie the Dun- 

 kirk or its Canaseraga equivalent, with a thickness of 250 

 to 500 feet. There is a persistent, but limited, Portage 

 fauna yielding eastward to the lower Chemung fauna of 

 the Cayuta shale into which these beds have been traced. 

 The next shale member, the West field shale (Chadwick 

 '19) is bounded below by the Laona sandstone and above 

 by the Shumla sandstone (Laona and Shumla, Chautau- 

 qua county; Clarke '03; Luther). These shales, named 

 from Westfield, Chautauqua county, are lithologically in- 

 distinguishable from the Gowanda beds and have a thick- 

 ness of 120 to about 200 feet. Here, too, is a persistent 

 Portage cephalopod fauna, yielding eastward wholly to 

 Chemung brachiopods. These and the Northeast shales 



