344 P. K liaymond — Age of the Tribes Hill Formation. 



Art. XXXVIII.— iTote on the Age of the Tribes Hill Forma- 

 tion; b}' Percy E. RAviroNi).* 



In a recent paper on the ao;e and relations of tlie Little Falls 

 dolomite of the Mohawk Valley, Ulrich and Cushiiigf have 

 separated the upper " f ncoidal beds " of Emmons from the 

 non-fossiliferous dolomite below, and have ju^iven them the 

 formation-name Tribes Hill. This formation they consider to 

 be of the age of the Lower Beekmantown, and state that it is 

 separated by an nnconforinity from the underlying dolomite, 

 which they assign to the Ozarkian. 



In a paragraph on the age of the Tribes Hill formation, 

 they state : '' That the Tribes Hill is younger than any known 

 Ozarkic formation is satisfactorily shown by the presence of 

 Asajphus and three or four other trilobites that ai-e wholly 

 unknown in Ozarkic faunas. The same is true of the Ribeirias; 

 and the Dalmanella ? wemplei also is a type that has not been 

 observed below the Canadian. With the exception of Eccyli- 

 omphahcs multiseptarins, the testimony of the gastropods is 

 less positive, very similar, though specifically distinct, forms 

 being found in Ozarkic faunas. The gastropods described by 

 Cleland 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." 



The writer has recently restudied the trilobites which occur 

 in the fauna described by Cleland from Fort Hunter, and finds 

 that the Asaphus canalis ? of that fauna is in no way related 

 to the Asaphus canalis of the Beekmantown of the Champlain 

 Valley, but belongs to that division of the Asaphidse in which 

 the hypostoma is not forked. The trilobite proves to belong 

 to the genus Asaphellus, and is redescribed as a species of that 

 genus in a paper now in press. The tiilobite descj-ibed by 

 Weller:}: from Columbia, New Jersey, as Isotelus canalis may 

 be the same species. 



Another Asaphid with an undivided hypostoma is the " Asa- 

 phus margin alis''"' mentioned by Collie§ as occurring in a zone 

 3,750 feet below the top of the Beekmantown at Beilefonte, 

 and as Ulrich and Cushing state, the fauna occurring with this 

 Asaphid in the Beilefonte section is so similar to that of the 

 Tribes Hill, that the two may safely be correlated. 



* Published by permission of the Director of the Geological Survey of 

 Canada. 



f Sixth Report of the Director of the Science Division, New York State 

 Museum, 1910, p. 97. 



X Pal. New Jersey, vol. iii, pi. 3, figs. 5, 6. 



gBull. Geol. Soc. Am., vol. xiv, p. 407, 1903. 



