Basin, younger than these Cambrian strata; and it is perfectly 
clear that the conglomerate and melaphyr series is newer than 
the granite, and therefore distinctly more recent than the 
Middle Cambrian. They are quite certainly Paleozoic, but 
whether as late as the Carboniferous strata in the Narragansett 
Basin is at least doubtful. The conglomerate and melaphyr 
and newer slates of the Nantasket area may be safely correlated 
with the same rocks in other parts of the Boston Basin; and it 
is hoped that, before the revision of the geology of the basin 
is completed, evidence will be forthcoming which will finally 
and definitely settle the question as to the age of these strata ; 
but for the present the problem must be regarded as unsolved. 
In January of this year (1892), Mr. Т. A. Watson found 
on Pleasant Beach, Cohasset, a smoothly rounded and evi- 
dently water-worn bowlder, between five and six inches in 
diameter, of a highly fossiliferous, compact, red (ferruginous) 
limestone. The fossils appear to belong wholly to two species, 
which have been identified by Mr. C. D. Walcott" as the two 
Lower Cambrian types Straparollina remota Billings and 
Hyolithes communis Billings. Although Mr. Watson was 
unable, after the most thorough search, to find a second speci- 
men of this limestone on the Cohasset shore, its Cambrian age 
made it seem highly probable that it had been derived from 
some point within the Boston Basin, and possibly within the 
Nantasket and Cohasset district, thus encouraging the hope 
that it would yet afford us the desired clue to the geological age 
of the Nantasket strata. But this hope has been dispelled ; for 
Mr. Watson has recently found several water-worn fragments 
of precisely the same kind of limestone, holding the same fossils, 
but not quite so abundantly, on the beach at Bass Point, 
Nahant. We can no longer doubt that this rock is a part of 
the Cambrian limestone of Nahant, although representing a 
more ferruginous and more conspicuously fossiliferous bed than 
any now exposed on that peninsula ; and the Cohasset speci- 
men must be regarded as a solitary glacial erratic. 
1 Proc. Biological Society of Washington, VII., 155. 
