248 BULLETIN! MUSEUM OF COMPARATIVE ZOOLOGY. 
various alternations, become successively finer. In this respect the 
sedimentary series of these two basins appear to conform to the arrange- 
ment observed in the case of the transgressing sea, as described by 
Hill. In the Narragansett Basin, however, this condition does not 
obtain. There the coarsest conglomerates occur at the top of the 
series. Local unconformities have been observed only in the Narra- 
gansett Basin but evidences of contemporaneous erosion occur in all 
three basins. Lenses occur in the sediments of each basin but their 
relations as regards original dip and strike are not clear. They seem, 
however, to be distributed along the same horizon or in parallel hori- 
zons. Limestones do not occur in the Roxbury series but in both the 
Norfolk and Narragansett Basins isolated outcrops of minor impor- 
tance have been found. In these cases, however, the limestone is not 
fossiliferous but is nodular and concretionary and evidently of second- 
ary origin. 
The strata in all three basins have been found to rest upon surfaces 
long subjected to subaerial decay. 
Lacustrine. The matrices of. the Carboniferous conglomerates, as 
described above, agree perhaps more closely with the lacustrine type 
than with the marine; for in the lacustrine type the sands are less 
clean, and less well sorted and rounded than is the case with marine 
sediments. Nevertheless, the lack of uniformity in composition and 
size of the grains is more marked than is suggested by the descrip- 
tive terms used in the table relative to lacustrine deposits. 
In the case of the pebbles, too, a similar comparison may be made. 
There is nothing distinctive about the color of lacustrine deposits. 
Russell states that lacustrine sediments are usually not red but that, 
should lake basins occur in regions of deep disintegration, like the 
southern Appalachians, the sediments deposited in such lakes would 
be red (a, p. 47-48). The Carboniferous sediments of eastern Massa- 
chusetts were formed in a region where there had been deep subaérial 
decay, so that if lacustrine sediments were deposited they would 
naturally have more or less red color. It has been shown that red 
colors are developed in the strata of each basin. 
The stratification of lacustrine deposits may be expected to resemble 
that of marine beds, except that the respective features would perhaps 
be less well developed. The stratification of the sediments under 
discussion is not well defined except in the finer textured members, 
but there the tendency is toward the production of more or less defi- 
nite bands, rather than of lenses. In the Boston and Norfolk Basins 
the succession of the sediments seems to be from coarse, toward 
See u ma eS 
