136 NEW YORK STATE MUSEUM 



of the Canadian underlies an aggregate thickness of nearly 4500 

 feet of Ordovicic limestone; and finally (7) that essentially the 

 same cycles of movement, of submergence and emergence, as are 

 used in distinguishing four Neopaleozoic systems, alsoi obtained in 

 the Eopaleozoic and suggest the propriety of a similar division of 

 the Eopaleozoic into four systems instead of two as heretofore. In 

 view of these facts we ask: Is the present indefinite separation of 

 the Eopaleozoic into Cambric and Ordovicic a reasonable and ade- 

 quate classification? Are these divisions coordinate in rank with 

 the Neopaleozoic, Mesozoic and Neozoic systems? Our answer to 

 these questions is clearly anticipated in the foregoing comments and 

 arguments. 



Age of the Tribes Hill formation. A few words remain to be 

 added respecting the age of the Tribes Hill. The formation is 

 certainly Postozarkic, but its position in the Canadian is less easily 

 determined. Except that we know the formation to be unconform- 

 able on the Little Falls and that the contact represents a consider- 

 able hiatus, we have only organic criteria to guide us in determining 

 the age. That the Tribes Hill is younger than any known Ozarkic 

 formation is satisfactorily shown by the presence of Asaphus and 

 three or four other trilobites that are wholly unknown in Ozarkic 

 faunas. The same is true of the Ribeirias ; and the D a 1 - 

 manella? wemplei also is of a type that has not been 

 observed beneath the Canadian. With the exception of E c c y 1 i - 

 omphalus multiseptarius, the testimony of the gastro- 

 pods is less positive, very similar, though specifically distinct, forms 

 being found in Ozarkic faunas. The gastropods described by Cle- 

 land from the upper chert zone of the Little Falls dolomite at Little 

 Falls are clearly Ozarkic types and hence are not referred to in this 

 paragraph. 



That the Tribes Hill is Canadian (emend. Ulrich) is unquestion- 

 ably indicated by its fossils ; and the same evidence is almost con- 

 clusive in assigning the formation to an early stage in this period. 

 With the possible exception of an orthoid shell, all the species so 

 far discovered in the Tribes Hill are distinct from those described 

 from the Beekmantown in the Champlain valley. They impress one 

 as older. This suggestion is confirmed when we compare the 

 Tribes Hill forms with faunas found in the Canadian in central 

 Pennsylvania. The nearest f acies — there are at least five and 

 probably six identical species — is found in the Bellefonte, Pa. sec- 

 tion about 3700 feet beneath the top of the Canadian. None oi the 

 succeeding faunules in the Bellefonte section are closely allied. 



