GUELPH FAUNA IN THE STATE OF NEW YORK 83 



var. americanum Foord, employing that author's distinctive designation 

 for American expressions of Sowerby's specimens. These specimens doubt- 

 less represent early growth stages ; one has 1 5 sharply developed somewhat 

 sinuous annuli in a length of 23 mm, another 10 in a length of 16 mm, a 

 third 24 in a length of 45 mm. The annuli are separated by rather deeply 

 concave depressions not always of equal width. Fine sharp longitudinal 

 striae, often clearly in two series, cross the surface, and these are cancelated 

 by much finer and obscure concentric lines. Nothing that would indicate 

 the modification of those characters in later growth has been observed. 

 Several large specimens, exceeding an inch in diameter and possessing 

 strong, rounded annulations, were obtained from the lower Shelby bed. 

 None were found in the upper horizon. 



Dr Whiteaves has reported the presence of this species in the Guelph 

 at Hespeler and Elora, where it seems to be rare and the surface characters 

 are not specially noted. It is also cited in the Geology of Wisconsin among 

 the Racine and Guelph fossils. Professor Hall x knew it only from the 

 lower beds at Waukesha and near Wauwatosa, Wisconsin. Its occurrence 

 at Yellow Springs and Cedarville O., is recorded by Hall and Whitfield in 

 Paleontology of Ohio, 2: 148. It is therefore evident that this species rises 

 from the lower Niagaran shales, where it is most common, into and through 

 the higher Niagaran beds in New York as well as in the west. 



Orthoceras bartonense is a shell from the Barton beds or 

 highest member of the Niagaran series at Hamilton Ont, which has been 

 described by J. W. Spencer 2 as distinct from D. annulatum in having 

 the annular crests marked " by swelling waves (giving a nodular appearance 

 on the margin)." This is the same variation which McChesney described 

 as O. nodocostatum 3 but which Hall seems to have correctly esti- 

 mated 4 as identical with O. annulatum. 



1 N. Y. State Cab. Nat. Hist. 20th An. Rep't, p. 351. 



2 Mus. Univ. Missouri. Bui. 1884. 1:60, pi. 7, fig. 7. 

 } Descr. Paleozoic Fossils, i860, p. 94. 



4 N Y. State Cab. Nat. Hist. 20th An. Rep't. expl. pi. 20. 



