RELATIONS OF CATARACT TO OTHER FAUNAS 291 



are restricted to the Medina, and 2 either pass into the Clinton or have 

 close relations with forms of this fauna ; the total number, however, that 

 persists into the Clinton is 4. These statements indicate that the 

 Medina is more closely related to the Cataract than to the Clinton. 



It should also be stated that the Medina is of the Appalachian prov- 

 ince, while the Cataract is either of the St. Lawrence or of the Arctic 

 realm. These waters came in over the continent from different oceanic 

 areas and accordingly have different organic associations. Hence the 

 similarity of the biotas can not be close, and this, with the marked differ- 

 ence in sedimentation, gives additional reason why considerable weight 

 is laid on the forms held in common, as showing that both formations 

 are the deposits of about one time. 



Relation to the Brassfield. — The Cataract may also be compared with 

 the Brassfield formation of Ohio and Indiana, as the two are clearly re- 

 lated, and also as both are of a limestone facies. The former has 76 

 species and the latter 140.^^ Between the two there are 24 forms in 

 common, and of these the following have the most significance in corre- 

 lation: Clathrodictyon vesiculosum, Acervularia (?) gracilis (in Ohio, 

 A. clintonensis) , Rhinopora verrucosa, Phcenopora ensiformis, Callopora 

 magnopora, Homotrypa (?) confluens, and Hehertella fausta. When 

 the two biotas are finally carefully compared with each other, there will 

 undoubtedly be added more significant forms, strengthening the view 

 that the Cataract and Brassfield are fairly close correlates in time. How- 

 ever, as these two faunas are not of the same epicontinental basin, one 

 can not expect a large percentage of the forms to be common to both ; the 

 Brassfield element came in from the Gulf of Mexico region, while the 

 Cataract migrated into Ontario through the Gulf of St. Lawrence em- 

 bayment across the Province of Quebec or came in from the Arctic. The 

 Brassfield is marked by the guide fossils Triplecia ortoni and StricJc- 

 landinia triplesiana, forms never seen in the Cataract, while the latter 

 has as its markers Helopora fragilis, Rhinopora verrucosa, Rhipidomella 

 circulus, Atrypa n. sp., and Ccelospira piano convexa. On the other hand, 

 both are closely related to the Clinton, for of the Cataract fauna fully 30 

 species pass upward and about the same percentage (40 per cent) from 

 the Brassfield. 



That the Cataract is a close correlate with the Medina has been shown, 

 and that it is equally so with the Brassfield can be brought out in still 

 another way. The Cataract fauna has 76 forms, and of these 22 have 

 no stratigraphic significance (those marked X and the Errant Annelida). 



» Foerste : Geol. Surv. Ohio, vol. vii, 1893, pp. 516-601, pis. 25-37a. 



