46 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165. 
The semislaty structure of the shaly sandstones also is evidence that 
they are not as late as the Chapman sandstones of the same region, 
which are not slaty at all, but are nearly flat and undisturbed by the 
cleavage which has affected all of the older rocks of the region. 
Fauna of 1099 D 2 and S. 
1. Monograptus (Graptolithus clintonen- 
sis) priodon. 
2. Cardiola interrupta. 
3. Coleolus tenuicinctum. 
4. Coleolus aciculum. 
5. Orthoceras cf. virgulatum. 
And a few other forme. 
The Graptolite shale is believed to be of Silurian age, but the fauna 
is a remarkable combination. Coleolus is as characteristically Devonian 
as Monograptus is Silurian. The specimens of Coleolus present the 
characteristics met with in the typical Mesodevonian forms of New 
fork. 
The Cardiola is certainty of the type of O. interrupta, which all over 
Europe is characteristic of the Silurian horizon. The three forms are 
certainly from the same rock formation. 
The facts deserve more exhaustive treatment -than can be given in 
this preliminary report. They confirm the conviction, already reached 
by the author from the study of the Black shales of the Devonian, that 
faunas which we are accustomed to call pelagic, and which we find 
generally in fine-grained, uniform, very thin-bedded, and often calca- 
reous shales, but usually in more or less siliceous shales, are locally of 
great taxonomic importance for the same geologic basin. Nevertheless, 
the faunas themselves contain species which have long stratigraphic 
range, and which can not be relied upon for close determination of 
chronologic position in the geologic series. 
As an illustration, in case we were to find Coleolus tenuicinctum, or 
any form closely allied to it, though it might be called specifically by 
another name, the containing rock would be referred on such evidence 
alone to the Devonian. If Monograptus priodon or any graptolite of 
this type of structure were to be found alone, it would certainly be 
referred to the Silurian system. When the association of the grapto- 
lite with a true Cardiola of the interrupta type occurs, it is impossible 
to assign the rocks a position higher than Silurian. 
The close resemblance of the specimens of Coleolus to the so-called 
embryo tubes of Endoceras protei forme of the Ordovician rocks 1 of 
New York, and to similar forms from the Bohemian Basin figured by 
Barrand, suggests the explanation that these peculiar fossils, which 
occur in strata of so widely separated age, were internal shells, com- 
parable to phragmocones, and with a chemical composition which 
escaped the solvent effects of the deeper waters in which they were 
probably fossilized. 
1 Pal. New York, Voi. I, pp. 213 et seq., and pis. 45, 46, 47, 
