-15- 



Straka and Webster, 1971, p. 406-412). In the Appalachian province, Idiognathodus 

 is the most abundant platform in the Pottsville and Allegheny Groups but is not 

 numerically important above the lowest part of the Conemaugh. The occurrence 

 of the genus at Bailey Falls is near the top of its stratigraphic range. 



Beds 1 and 2, which are exposed at the south end of the quarry as 

 well as in the north bluff of the Vermilion River and in the Route 51 road- 

 cut south of the Illinois River, contain abundant Gondolella . Because of 

 its spotty stratigraphic occurrences, Gondolella appears to be environmentally 

 restricted and apparently indicates a distinct biofacies. The genus is not 

 known from Appalachian faunas. 



An interesting occupation is the reconstruction of assemblages based 

 on the species listed in table 1. Abundances range from approximately 140 

 specimens per kilogram up to 870 per kilogram. WHILE COLLECTING, ALWAYS BE 

 ALERT TO OVERHANGING ROCKS ABOVE AS WELL AS TO PERSONS WHO MAY BE BELOW YOU 

 ON THE SLOPE. PLEASE BE CAREFUL! 



LOCATION OF THE NATURAL ASSEMBLAGE 

 COLLECTING ZONE AT BAILEY FALLS 



One of the most prolific localities for collection of natural conodont 

 assemblages, outside of Montana (Scott, 1942), and the topotype locality for 

 Duboisella typica Rhodes and Scottognathus typicus (Rhodes) is the Bailey 



Falls section. Ernest P. DuBois 

 (1941) was the first to publish 

 notice of the occurrence of natural 

 assemblages here. In the same re- 

 port, he recognized natural assem- 

 blages that consist of a pair of 

 platform elements, a pair of "bry- 

 antodids," and several pairs of 

 hindeodellids, all in a linear series. 

 The form is Scottognathus (Rhodes) 

 1952 (fig. 7). DuBois also identi- 

 fied one speciment that exhibited 

 three platform elements. By 1942, 

 DuBois had collected between 75 and 

 80 assemblages from a total of 300 

 pounds of shale. He described the 

 stratigraphic location as "fissile 

 black shales which lie just below 

 the La Salle limestone of McLeans- 

 boro (Pennsylvanian) age. Under- 

 lying the black shale is a seam of 

 coal which varies from one to several 

 inches' in thickness. The shale mem- 

 ber is about 18 inches thick but tends 

 to vary from one area to another." 

 The precise stratigraphic location of 

 the most productive zone found by 

 Ave in and Norby is 13 to 19 inches 



Fig. 7 - Natural assemblage of 

 Scottognathus typicus 

 (Rhodes) illustrating 

 simple scatter after 

 contraction of assem- 

 blage (X25). See also 

 figure 10. 



(Continued on page 22) 



