Cincinnatian and Lexington Fossils 31 



the median fold and the intermediate grooves have very much the 

 same appearance as in Zygospira nwdcsta. While the bifurcation 

 of the primary plications, or the intercalation of additional ones, 

 is the chief character usually relied upon in diagnosing this species, 

 too much weight must not be given to this feature, since it is not 

 •constant, and numerous specimens may be collected at the typical 

 horizon, in which there is no evidence of bifurcation. Among the 

 four primary plications on the median fold, it is the lateral plica- 

 tions, and not the two median plications which frequently are bifur- 

 cated. Bifurcation of one or two of the lateral plications on each 

 side of the median fold is not rare. Occasionally, even the two 

 median plications on the fold are bifurcated toward the anterior 

 margin of the shell, or one or two small plications are inserted near 

 the anterior end of the median groove. Some of these specimens 

 attain a length of 13 mm. Only the larger specimens are likely 

 to show evidence of frequent bifurcation. 



Although only a part of the specimens in the upper Fairmount 

 show evidences of bifurcation it should be stated that it is only 

 at this horizon that bifurcation becomes conspicuous. In the Mount 

 Hope bed, at Cincinnati, Ohio, Vevay. Indiana, and a mile north 

 ■of Mason, Kentucky, specimens occur with only 5 broad, angular, 

 lateral plications, and wiih a prominent fold and distinct, broad 

 sinus, but with no I )i furcation of the plications. These specimens 

 undoubtedly are the ancestral forms of t}'pical Zygospira cincin- 

 naticnsis from the upper Fairmount. The type, however, orig- 

 inated already in the middle Eden, where specimens with 5 broad, 

 angular lateral plications are found locally, for instance at Vevay. 

 Indiana. 



Catazyga uphami — australis, var. nov. 



(Plate II, tigs, ig A.B; Plate III. f^gs. 14. A,B.C.) 



In the Camp-nelson division of the High-bridge formation, at 

 High Bridge, Kentucky, there is a species of Catazyga evidently 

 closely related to Catazyga uphami, described from a somewhat 

 higher horizon, in IMinnesota. In Kentucky, this species of 

 Catazyga is associated with Ortliis friccnaria, Hehertella hellaru- 

 gosa, and Rafinesqnina minncsotcnsis. 



The Catazyga from High Bridge, Kentucky, agrees with the 

 typical form of Catazyga uphami in the number of radiating plica- 



