234 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
among them, Ogygiocaris dilatata, Nileus armadillo, Trinucleus cos- 
einorrhinus, all of which are found in the zones of Climacograptus 
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 Didymograptus geminus shows definitely that 
it antedated there the first appearance in Norway, for in the latter 
country it is found first in strata resting upon those containing D. 
geminus. 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 evidence 
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 a8, among them the Ogygio- 
carts dilatata itself. In Jemtland Ogygiocaris is found in the zones of 
both Climacograptus putillus and Nemagraptus gracilis and serves to 
connect the Nemagraptus zone with the first Echinosphaerites zone 
in Norway (4 af). 
NoORMANSKILL. 
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 
Normanskill 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 above the typical Chazy, making it a member of his Blount 
group, which he places between the Stones River and the Lowyville. 
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. 
