562 PROCEEDINGS OF THE ACADEMY OF [DeC, 



is now grouped with the other layers down to the Onondaga under 

 one formational term, Marcellus.- 



As used by Vanuxem,^ the term Marcellus apparently embraced 

 a still higher shale of gray color. This latter was given a separate 

 name by Clarke and Luther who in 1904 called it the Cardiff shale.'* 

 In the type region (on the Tully quadrangle) the change from the 

 Marcellus is most gradual while above the Cardiff is defined as 

 terminating some 20 feet below a thin band of limestone.^ This 

 limestone is grouped with the 20 feet of shale below and some hun- 

 dreds of feet above under a single formational term, Skaneateles. 



These general stratigraphic relations appear to hold good for 

 central Onondaga County, but on tracing the formations westward 

 deviations from the type section are noticed. It is now proposed 

 to present the evidence for these deviations. 



Just south of Mottville, on the Skaneateles quadrangle, occurs 

 a fossiliferous zone which is well displayed along the outlet of Skane- 

 ateles Lake. The section at this point shows a thickness of about 

 25 feet. In the lower part the shale is gray and thinly bedded 

 with small fossils numerous. Above come small concretions and 

 a limy band full of crinoid fragments. This latter is in turn overlaid 

 by a rather coarse and thickly bedded shale, also quite fossiliferous.^ 

 These strata are not here exposed in continuous section with any 

 easily recognized reference plane. It was with the intention of 

 ascertaining their position in the shale mass that the writer under- 

 took to follow these beds east and west from the Mottville locality. 



For the sake of simplicity the term Mottville member will be 

 used as a provisional designation for the limy crinoidal band and 



2 N. Y. State Museum Bulletins 63, p. 14, and 82, pp. 42, 43. 

 ^ Nat. Hist, of N. Y., Geologj', III, comprising the Survey of the Third Geo- 

 logical District, 1842, pp. 146, 147. 



4 N. Y. State Museum Bulletin 63, p. 16. 



5 N. Y. State Museum Bulletin 82, pp. 45, 46. 



" These layers were apparently well known to Vanuxem ; see Geology of the 

 Third District, p. 154. Speaking of Cayuga Lake, he says: "The first rock 

 going south on the lake, after passing the low clayey ground to the south of 

 Springport, may be considered as the dividing Hne between the Marcellus shales 

 and the Hamilton group. It is a dark slaty fossiliferous shale, with numerous 

 individuals of the Orthis umbonata of Mr. Conrad, but usually small, associated 

 with the Limitary orthis (O. hmitaris) also numerous, etc. It shows about 

 six feet of a brownish black impure limestone. This pai't forms the small rise 

 about half a mile or more below Levana. It appears in the road from Springport 

 to Levana, at Crise's brook; on the road to Auburn from Springport, two miles 

 southwest of Half-acre; to the northeast of Skaneateles on the road to Marcellus, 

 and on the north side of Pompey hill, etc." 



Though this description makes no mention of the Mottville locality, it shows 

 quite clearly that its author was familiar with many of the other good exposures 

 of these strata. 



