163 



wick by the Laurentian and Norian deposits of that province, 

 and by the same formations in central Newfoundland. The 

 Huronian is well developed about and upon these more ancient 

 terranes in Newfoundland, and, likewise, in New Brunswick ; 

 and rocks clearly recognizable as Huronian occur at intervals 

 along the coast of Maine, serving to connect those last men- 

 tioned with the well-known area in Eastern Massachusetts. 

 There is a broad Montalban belt which extends without 

 interruption from Long Island Sound, along the north-west 

 side of the Massachusetts Huronian, through New Hampshire 

 and Maine, to New Brunswick ; and rocks of this age ap- 

 pear on Newfoundland, between the Laurentian rocks in the 

 middle of the island and the Paleozoic along the western coast. 

 Crystallines having Montalban characters are well developed 

 over the south-eastern half of Nova Scotia ; and these, I ven- 

 ture to suggest, may be continuous, along the submarine ridge 

 already pointed out {ante, p. 7), with the Montalban of 

 south-eastern Massachusetts. 



Here, then, we have, indistinctly outlined, the great ge-anti- 

 clinal, the erosion of which has given rise to the Gulf of Maine. 

 The eastern side of this eroded anticlinal, borne beneath the 

 waves, is represented by the submarine ridge connecting New- 

 foundland and Nova Scotia with Cape Cod. The erosion of the 

 Gulf of Maine was substantially complete before the beginning 

 of Paleozoic time, and this fact alone shows that an enormous 

 period elapsed between the close of the Montalban era and the 

 deposition of our Primordial slates. 



SHAWMUT GROUP. 



The rocks included in the Shawmut group are those commonly 

 known in the vicinity of Boston as the breccia and the amygda- 

 loid. They are found chiefly within a radius of ten to fifteen miles 

 of Boston, but occur also on Marblehead Neck and the neighbor- 

 ing islands and in the basin of the River Parker. They are 



