414 The Upper Devonian Deposits of Maryland 



Beds Containing the Ifliaca Fauna. — The beds coDtaining the Ithaca 

 fauna so closely resemble those of the underlying division lithologically, 

 that it has not proven practicable to separate them upon the map of the re- 

 gion. In general the shale tends to be somewhat softer than that of the 

 lower division and some beds break M'ith a more irregular fracture, while 

 the proportion of sandstone is somewhat smaller. In a single section in 

 Thompson Township, Fulton County, Pennsylvania, in the extreme north- 

 eastern part of the area studied, the upper limit of the Woodmont member 

 has been so drawn as to include several conglomeratic sandstones. No 

 conglomerates have been observed in this member Mest of that point. 



East of Sideling Hill the top of the division is frequently formed by a 

 bright red bed which, in its lithological features, closely resembles sedi- 

 ments of the Catskill formation. Some of the lower beds have also a 

 reddish tone. 



The Ithaca fauna ranges through a thickness of 1000 to 1100 feet in 

 the vicinity of Hancock. Farther west the fauna becomes more re- 

 stricted and finally vanishes west of Green Eidge where it is replaced by 

 the Naples fauna in the same strata that contained the Ithaca fauna 

 farther east. 



The Ithaca fauna differs greatly from that contained in the underlying 

 beds. Brachiopods occur in profusion, while many large pelecypods of 

 entirely different genera from those found in the Naples fauna are pres- 

 ent. A list of the species observed in these beds is given in the table of 

 distribution. 



The beds containing the Ithaca fauna may be subdivided into two 

 faunal zones, a lower termed the Cladochonus-Rcticidaria Iwins zone and 

 an upper, the Liorhynchus globuliforme zone. 



Genesee-Woodmont Boundary. — When the Genesee is present the 

 lower limit of the Woodmont member is defined by the contrast between 

 the olive-green color of the Woodmont shale and the black or brown color 

 of the Genesee shale. The transition from the Genesee to the Woodmont 

 is, however, not very abrupt, so that the precise plane of division is not 

 always determinable, some of the beds being more or less transitional at 

 many places. 



