Crosby.] 
116 
[December 15, 
sometimes be regarded as annelid trails, but in other cases they 
are irregularly branched in a way that would be impossible with 
worm grooves, but is very suggestive of smooth, slender fucoids. 
They lie in the plane of the bedding, and are in part very sim- 
ilar to the Palaeochorda marina of Emmons from Washington 
County, New York; but, in not being crenulated, they are 
entirely unlike his Nereites (Nereograpsus) from Waterville, 
Maine. The slate in which the impressions occur is a compact, 
grayish black variety, with thin arenaceous patches, ripple-marks 
and eroded mud-surfaces. 
According to Professor Hitchcock, the slates of Narraguagus 
Bay are also fossiliferous, containing “an Orthis, encrinal joints 
and supposed corals ”; and slates which he assigns to the same 
horizon, on Foster’s Island, off Machiasport, contain undetermined 
Khynchonellae. Professor Hitchcock predicted the discovery of 
Paradoxides on Ship Island, in Narraguagus Bay; but unfor- 
tunately no characteristic fossil has yet come to light in any part 
of this formation. I think, however, that it will be admitted 
that the general aspect of the organic remains so far found, in- 
dicates a j^osition low in the Cambrian ; and in support of this 
conclusion, I desire to present one argument entirely independent 
of the foregoing considerations. It is well known that between 
Machias Bay and New Brunswick, enclosing the waters of Cob- 
scot and Passamaquoddy Bays, there is a well defined basin of 
Devonian and Silurian (Upper Silurian) Beds, holding character- 
istic fossils. Like the slates in Narraguagus and Frenchman’s 
bays, these are extensively intersected by both basic and acidic 
eruptives, in well defined dikes. But there is this important 
difference, in Frenchman’s Bay the exotics are coarsely crystalline 
diorite and granite, while in the Silurian and Devonian basin the 
diorite is very much fi?ier grained and there is no true granite, 
but, instead, felsite and quartz porphyry. 
This difference in the texture of the intrusives in the two dis- 
tricts, undoubtedly corresponds to a difference in age, those to 
the westward being the older ; and from this conclusion the in- 
ference flows naturally that there is a like difference in the ages 
of the intersected formations. 
