SPECHTS FERRY BRYOZOAN FAUNA 5 



D. praenuntia echinata is abundant in the Trenton equivalents in the formation but 

 not noted from the Black River, and B. winchelli spinulosum was found by Fritz 

 only in Trentonian beds in the formation. In view of their stratigraphic distribution 

 in the Ottawa Formation, these four species considered collectively may possibly 

 be somewhat more indicative of Trentonian age than of Blackriveran age. The most 

 striking difference between the bryozoan faunas of the Spechts Ferry and the Ottawa 

 Formation is the great abundance of Stictoporella Ulrich in the Spechts Ferry and 

 its apparent absence in the Ottawa fauna. 



Loeblich (1942, p. 417-435) recognized two species, Dekayella praenuntia 

 echinata and Batostoma winchelli , in the Bromide Formation of Oklahoma that are 

 found also in the Spechts Ferry. Loeblich recorded these species from the upper 

 25 feet of the formation in strata that generally are considered to be Blackriveran 

 in age. 



Some Spechts Ferry species appear in faunal lists of formations of Middle 

 Ordovician age. Admittedly, more references in which these species are listed 

 could be included here. Prasopora simulatrix orientalis, a comparatively rare 

 species in the Spechts Ferry, presumably is more indicative of Trentonian age, 

 although Coryell (1916, p. 265, 266) noted this species, as well as Batostoma 

 winchelli spinulosum, in Black River and Trenton strata in New York. Caley 

 (1936, p. 27) established two paleontologic zones in the Trentonian rocks of 

 Manitoulin Island, the lower of which, 40 feet thick, is termed the P. simulatrix 

 orientalis zone. According to Caley, this species is restricted to these beds on 

 Manitoulin Island. In addition to P. simulatrix orientalis , Caley (1936, p. 29) 

 recorded Dekayella praenuntia echinata and B. cf. winchelli from the Trenton of 

 Manitoulin Island, which species are found also in the Spechts Ferry. Wilson 

 (1921, p. 31) listed B. winchelli as a common fossil in the upper Leray beds of 

 late Blackriveran age in the Ottawa Valley and P. simulatrix orientalis as an ex- 

 ceptionally common species in the lower beds of the Rockland of early Trentonian 

 age from the same area. In an earlier publication, however, Wilson and Mather 

 (1916, p. 49, 55) noted B. winchelli in both Blackriveran and Trentonian rocks of 

 the Kingston area in southern Ontario. Finally, Sproule (1936, p. 104) recognized 

 P. simulatrix orientalis from Coburg beds of Trentonian age in New York and south- 

 ern Ontario. 



This discussion indicates that on the basis of its bryozoans the age of 

 the Spechts Ferry cannot be established definitely as either Blackriveran or Trenton- 

 ian. This situation results primarily because the known stratigraphic ranges of 

 its widely distributed species span the Black River-Trenton boundary and because 

 there is inadequate knowledge of Middle Ordovician bryozoan faunas. 



Acknowledgments 



This study is part of a major investigation of the Middle Ordovician strata 

 of Illinois by the Illinois State Geological Survey. I am grateful to Charles W. 

 Collinson and H. B. Willman of the Survey for discussions of the stratigraphic 

 problems and for direction to some of the collecting localities. Professor Emeritus 

 J. J. Galloway of Indiana University assisted in some identifications. Technologic 

 facilities, including photography by George Ringer of the Indiana Geological Survey, 

 were provided by Indiana University. 



