234 bulletin: mtjseltm or comparative zoology. 



among them, Ogygiocaris dilatata, Nileus armadillo, Trinucleus cos- 

 cinorrhinus, all of which are found in the zones of Climacograptvs 

 putillus and Nemagraptus gracilis in Jemtland. 



It would seem from the comparison of sections that Echinosphaer- 

 ites appeared in northern Europe first in Oeland and migrated thence 

 into Norway and Russia. Its occurrence in Oeland in strata older 

 than those containing Didymograptiis geminus shows definitely that 

 it antedated there the first appearance in Xorw^ay, for in the latter 

 country it is found first in strata resting upon those containing D. 

 gejninus. In Russia the sequence of faunas, Echinosphaerites first 

 and then Echinosphaerites and Christiania, is exactly the same as in 

 Norway, strongly suggesting that the Echinosphaerites did not reach 

 that country sooner than it did Norway. There is physical e^^dence 

 in Russia of an interruption of sedimentation after the Kunda forma- 

 tion was deposited, while there is but slight evidence of a break be- 

 tween the Reval and the Kuckers. This, coupled with the faunal 

 evidence, particularly the total absence of the Ogygiocaris fauna in 

 Russia, indicates such a correlation as I have shown in the table. 



The Ogygiocaris fauna is Norway is found best developed in 4 aa 

 but many of the species pass over into 4 a/3, among them the Ogygio- 

 caris dilatata itself. In Jemtlaiid Ogygiocaris is found in the zones of 

 both Climacograptus pidillus and Xemagraptus gracilis and serves to 

 connect the Nemagraptus zone with the first Echinosphaerites zone 

 in Norway (4 a/3). 



NORMANSKILL. 



The Didymograptus geminus fauna has not yet been identified in 

 America, but the Nemagraptus gracilis fauna is well known from the 

 Normanskill shale of New York. At the type-locality, however, the 

 Normanskiir shale is very much faulted, folded, and twisted, and its 

 correlation with the formations of the standard section is not yet 

 established. Ruedemann at first considered it to be of early to Middle 

 Trenton age but later inclined to correlate it with the Black River. 

 Ulrich (119) has considered it still older, placing it below the Low- 

 ville, but abo\'e the typical Chazy, making it a member of his Blount 

 group, which he places between the Stones River and the Lowville. 



In Virginia typical Lower Dicellograptus faunas (Nemagraptus 

 gracilis zone) have been seen in sections where the sequence is normal 

 at two localities, but in neither is the evidence fully established. In 

 looking over material collected by Drs. E. O. Ulrich and George W. 



