TWENHOFEL: EXPEDITION TO THE BALTIC PROVINCES. 31] 
17. Isotelus robustus. 
18. Platylichas cicatricosus. 
19. Proetus ramisulcatus. 
STRATIGRAPHIC AND FAUNAL RELATIONS OF THE BoRKHOLM FoRMA- 
TION TO THE LYCKHOLM. 
There are no reasons for believing that the Borkholm is other than 
conformable on the Lyckholm and directly continuous thereto. 
Furthermore, the faunas are essentially identical and at least fifty- 
three of the ninety-five Borkholm species occur in the Lyckholm. 
Several of these common species belong to the genus Halysites. I 
believe it will ultimately be found necessary to unite several of these; 
but this will not change the strong faunal similarity. Each formation 
contains many species of Silurian aspect; this is shown to a greater 
degree in the Borkholm, where Silurian forms are conspicuous and 
abundant, but the Ordovician expression dominates. 
TimME EQUIVALENTS OF THE LYCKHOLM AND BoORKHOLM. 
At present these can be given in only a general way. When the 
collections have been secured and submitted to a careful study itis 
hoped to give a detailed correlation. 
Considered as a whole the faunas bear an aspect not generally fami- 
liar to American stratigraphers. The large Porambonites; the asso- 
ciation of Halysites and members of the Heliolitidae with large 
Hormotomas, Maclureas, and Subulites; and the abundance of large 
Triplecias are faunal groupings not occurring in America, yet certain 
associations are similar and the faunas have many components which 
are present in American deposits, the writer being constantly im- 
pressed with certain striking similarities. 
The points of contact with American sections are greatest in num- 
ber in the Anticosti formations,! where the facies and faunal associa- 
1The Anticosti section is, figuratively speaking, on the frontier of the American Upper 
Ordovician and Silurian, and hence would be most likely to show the greatest faunal similari- 
ties to the strata of like age of northwestern Europe. The Anticosti section consists of eight 
formations of which the lower four are Ordovician and the upper four Silurian. Named from 
the summit downward, the formations are as follows. 
Silurian Chicotte. Ordovician Ellis Bay 
1223 feet Jupiter River. 939 feet. Charleton 
Gun River. English Head 
Becsie River. Macasty. 
