p. E. liaymond — Age of the Tribes Hill Formation. 345 



Another Asapliid of the Tribes Hill is tlie Asaphus con- 

 ■vexus Cleland = Bathyii7'%is levis Cleland = lUeenurus colwm- 

 hiana Weller. The narrow axial lobe of the pygidiuni, as well 

 as the genei'al shape, show that this species is more closely 

 related to Symphysurns than to the typical species of Illm- 

 nurus. After nntangling the synonymy this species appears 

 to emerge nnder the name Symphysurus convexus (Cleland). 



Except for a few species of Nileus, information about Asa- 

 phids with nnforked hypostomas is practically wanting in 

 America, though several species are known. For knowledge 

 of the stratigraphic value of this group, we must, then, turn to 

 Europe, where numerous species are known in Great Britain, 

 France and Scandinavia. In all these countries, Asaphellus 

 and Symphysurus occur together in the Tremadoc, above the 

 Cambrian and below the range of Asaphids with forked hypos- 

 tomas. The only Asaphellus previously known from the 

 American continent is that described by Matthew* from strata 

 immediately overlying the Cambrian on Cape Breton island. 

 The fauna found there with the Asaphellus is a small one, 

 and not closely allied to the one found at Fort Hunter. 



Bi'oggerf has pointed out that the Tremadoc {^Euloma-Niobe 

 fauna) occurs in America, but its exact position and full fauna 

 have never been worked out. Brogger listed a number of 

 species indicating this fauna in Newfoundland and in the con- 

 glomerates at Point Levis. Niobe morrisi (Billings) was men- 

 tioned by him as representing the Asaphids with unforked 

 hypostoma, and to this may be added Asaphus illcenoides 

 Billings, which is a Sym.physurus, and Asaphus goniurus 

 Billings, a Megalaspides. These are, in turn, associated with 

 Dicelocephalus magnificus Billings, and, therefore, older than 

 Beekmantown. Asaphellus and Symphysurus seem, then, to 

 be genera characteristic of the fauna immediately following 

 the Cambrian. 



With Asaphus removed from the list of trilobites of the 

 fauna of the Tribes Hill the aspect is not very modern, and 

 with the gastropods only specifically distinct from those of the 

 Ozarkian, the whole fauna seems as much Ozarkian as Beek- 

 mantownian. 



According to Ulrich and Cushing, the stratigraphy shows 

 that the Tribes Hill formation is younger than the Hoyt forma- 

 tion which carries the Saratogan fauna described by Walcott. 

 The fauna of the Hoyt limestone is stated to be similar to that 

 of the Gasconade chert of the Ozarkian of Missouri. The top 

 of the Gasconade chert is from 120-475 feet below the top of 



*Bull. Nat. Hist. Soc, New Brunswick, vol. iv, part v, 1902. 

 ■f-Nyt. Mag. f. Naturvidensk. , vol. xxx, 1896, p. 164. 



Am. Jour. Sci. — Fourth Series, Vol. XXX, No. 179. — November, 1910. 

 23 



