vvilliams] FAUNAS OF THE SHERIDAN SANDSTONES. 47 
SHERIDAN SANDSTONE. 
The Sheridan sandstone is described, in its lithologic features, in 
Part II of this report (p. 132). In its appearance it is a peculiar rock, 
looking like an ordinary sandstone of various degrees of fineness and 
in its coarsest state a pebbly conglomerate. 
The color is greenish gray to rather dull brown. When closely 
inspected it is found to be composed of soft and hard rocks, both 
rounded and angular — quartz and feldspar; jasper, slate, and argilla- 
ceous shale, green, red, and black; and fragments of fossils, corals and 
crinoids, but particularly pieces of brachiopods of size large enough 
to recognize. 
The most conspicuous feature about the rock is the angular pieces 
of black slate, which at first suggest fragments of carbonaceous matter, 
but are evidently fragments of the more ancient slates. What is 
petrographically important about them is that igneous materials also 
are associated with them, emphasizing their close association in origin 
with the tuffs and volcanic ash beds with which they are stratigraph- 
ically associated. 
The evidence is clear, as Is brought out in Dr. Gregory's report, 
that the Sheridan sandstones were formed at a time of, and in a region 
subjected to, violent volcanic eruptions. 
Sheridan Plantation. — The typical exposure (1097 A) of this sand- 
stone and its fauna is found in Sheridan Plantation, south of the river, 
on the road from Ashland to Presque Isle, a few rods north of the 
Sheridan southern line. 
Fauna of 1097 A. 
1. Strophomena rhomboidalis. 
2. Orthothetes stibplanus. 
3. Anoplotheca hemispherica. 
4. Leptsena transversalis. 
5. Orthis, several species. 
6. Stropheodonta sp. 
7. ? Atrypa reticularis. 
8. ? Platystoma sp. 
9. Corals, several species. 
10. Spirifer cf. radiatus. 
A second exposure (1097 E) is on the right bank of the Aroostook 
River a short distance below the mouth of Alder Creek. Here the 
characteristic sandstone is seen with fragments of fossils, but none 
gathered were perfect enough to make out the species. 
Other exposures of the same sandstone were seen, one (1097 F) south 
of the same road at the Frenchville store and church, and another 
(1097 H) at Alley's grindstone quarry on the Alley farm, on the right 
bank of Aroostook River about a mile west of the east line of Sheridan 
Township. Fragments of fossils were seen in these several exposures, 
but they were mainly too much broken for identification. At Alle} 7 's 
grindstone quarry an undetermined brachiopod resembling Cyrtia, 
but with punctate shell, was seen (catalogued as No. 504), which is also 
present in the shales at Ashland (1098 C 3). 
