44 
CONTRIBUTIONS TO THE GEOLOGY OF MAINE. 
[BULL. 165. 
ping at Jonesboro, in southern Illinois, and refer the fauna to the 
Corniferous group. 1 
1. Pleurodictyum problematicum Goldf. ? 
2. Baryphyllum ?? arenarium M. & W. 
3. Zaphrentis (sp. undt.). 
4. Orthis sp. (cf. 0. musculosa) . 
5. Strophomena (Strophodonta) sp. ? 
6. Strophomena (Strophodonta) sp. ? 
7. Productus exanthematus Hall ?? 
8. Spirifer perextensus M. & W. 
9. Spirifer paradoxus Schlot ?? (sp.). 
10. Odontocephalus — ? 
11. Dalmanites (Odontocephalus) segeria 
Hall? (sp.). 
NEW PALEOZOIC FAUNAS FROM AROOSTOOK AND SOMER- 
SET COUNTIES, MAINE. 
The new Paleozoic faunas from these counties include the faunas of 
(1) the Aroostook limestone, (2) the Graptolite shales, (3) the Sheridan 
sandstone, (4) the Ashland shales, (5) the Ashland limestone, (6) the 
Square Lake limestone, (7) the Chapman sandstone, (8) the Moose 
River sandstone, and (9) the Mapleton sandstone. 
AROOSTOOK LIMESTONE. 
Under the above name are grouped the calcareous shales and slates 
covering a large part of the eastern township of Aroostook County. 
Their petrographic and structural characters are described by Dr. 
Gregory (p. 141, et seq.). The Aroostook River cuts them from Wade 
Township to its junction with the St. John. They were referred to 
the Upper Silurian by Hitchcock, 2 and later writers have not succeeded 
in getting much more definite knowledge of their age. 
The few fossils found in them indicate as great age as the Clinton, 
and comparison with neighboring rocks to the west confirms this gen- 
eral estimate. Cleavage has affected them to such an extent that it 
has produced real slaty cleavage occasionally, and in most cases has 
so much disturbed the original structure by cross-cleavage planes as 
» to make the original bedding difficult to discover, except where bands 
of limestone appear. 
The few fossils obtained are fucoids and trails and markings of 
worms or some other marine animals. Specimens in light-greenish 
shales at Caribou and Presque Isle resemble the forms figured in the 
New York reports as Buthotrephis gracilis from the Clinton shales. 
Traces of Acidaspis are also seen, and in calcareous layers in Presque 
Isle and Mapleton Bilobites bilobus, an Orthis close to 0. elegantula, 
and JVucleospira pisiformis have been discovered. 
These all indicate that the formation was as late as Eosilurian, and 
not as early as Ordovician (Lower Silurian). If this interpretation 
1 Geol. Survey Illinois, Vol. Ill, Geology and Paleontology, pp. 407-418. 
2 Sixth Ann. Rept. Secretary Board of Agriculture, Maine, 1861. 
