30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



*Coosia alethes 



Coosia robusta 



Coosia, sp. undet. 



Coosina ariston 



Coosina, sp. undet. 



Crepicephalus buttsi 



Crepicephalus cf. convergens 



Crepicephalus cf. scissilis 



Crepicephalus, sp. undet. No. 1 



Crepicephalus, sp. undet. No. 2 



Kingstonia inflata 



Llanoaspis walcotti 

 *Maryvillia arion 



Meteoraspis mutica 



Meteoraspis, sp. undet. 



Pemphigaspis, sp. undet. 



Terranovella dorsalis 

 * Tricrepicephalus thoosa 



Undet. cranidium No. 1 



Fossils from the U.S.N.M. localities 24m, 104, 121a, 123b, 125 and 

 125a were certainly all collected in the Rogersville area from the 

 lower limestone member of the Nolichucky formation, hence from the 

 horizons here designated cnk, cnm, and cnn. 



FAUNA OF THE APHELASPIS ZONE 

 The faunal succession in the Aphelaspis zone is particularly well 

 developed in Tennessee and was studied in great detail in several 

 sections. 



At some of the localities there is no gap in fossiliferous beds between 

 the Crepicephalus and Aphelaspis zones, hence the change from one 

 fauna to the other could be thoroughly investigated. It was shown in 

 the preceding section that the latest Crepicephalus zone faunule is 

 characterized by species of Coosia, Crepicephalus, Tricrepicephalus, 

 Blountia, and Kingstonia, in addition to Maryvillia arion and Terra- 

 novella dorsalis. Other genera, such as Amiaspis and Llanoaspis, are 

 occasionally present. At Russell Gap, a faunule that is considered to 

 belong in the Aphelaspis zone appears about 3 feet above the typical 

 Crepicephalus fauna, in a succession of massive limestone beds of 

 uniform lithology. This basal Aphelaspis zone faunule (loc. cno/14) 

 yielded several species of trilobites representing a holdover of Cre- 

 picephalus zone forms with the addition of new elements, which had 

 certainly evolved elsewhere since no possible immediate ancestors 

 occur in the local Crepicephalus fauna. The Crepicephalus zone genera 

 Tricrepicephalus, represented by an undetermined species, and 

 Coosella, represented by Coosella perplexa, are associated with the 

 typical Aphelaspis zone forms Aphelaspis cf. A. lata and Cheilocephalus 



