98 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
Neponset region are part of the conglomerate formation, the area has 
the shape of a somewhat distorted obtuse triangle, with a base nearly 
thirty miles long and an altitude of twelve or thirteen miles. The 
total area, therefore, is about 120 or 130 square miles, of which the 
doubtful slates constitute more than one-half. 
NEIGHBORING CONGLOMERATES.— Other Areas. South of the Blue 
Hill Range in the so-called Norfolk County Basin lies another rela- 
tively narrow belt of sediments which bear many resemblances to 
the members of the Roxbury series. These rocks are known to be 
connected through a narrow pass at Sheldonville with the conglom- 
erates and other sediments of the Narragansett Basin. The latter 
series occupies a large part of the state of Rhode Island and includes 
a portion of southeastern Massachusetts but it is separated from the 
Norfolk Basin sediments, except at Sheldonville, by an area of erys- 
talline rocks. 
Small areas of conglomerate occur in the basin of the Parker River 
in Essex County, at Bellingham, and Harvard, Massachusetts, and at 
Woonsocket, Rhode Island. 
Lithological Relations. The Norfolk Basin sediments consist of 
arkoses, coarse and fine conglomerates, sandstones, and slates that are 
much like the Roxbury series, though it may be said that on the whole 
the former have a more marked tendency toward a red color. The 
pebbles of the conglomerates in the two regions are composed of the 
same substances, with the exception of the Blue Hills porphyry, which 
is said to occur on the south side but does not certainly appear on the 
north side of the Blue Hill Range. Moreover, the only organic 
remains thus far discovered in the Roxbury series are casts of tree 
trunks that are similar to forms found in certain portions of the Norfolk 
Basin. It has been stated that on the north no direct connection has 
been traced between the Norfolk Basin sediments and the Roxbury 
series. It was noted, however, that near Green Lodge (Plate 7, 
Dedham IV, E 16), about in the line of the Blue Hill Range projected 
westward, there is a limited outcrop of sandstone. The rock in ques- 
tion is greenish gray in color, silicious and similar to some members 
both of the Roxbury and Norfolk Basin series. But it is mych indu- 
rated and is penetrated by quartz veins. Possibly it may be a remnant 
of some earlier formation that furnished material to the conglomerates 
and formed part of the floor upon which they were deposited. It may 
be connected with the older slates or it may represent a sandy mem- 
ber of the conglomerate series. ‘Thus no determinative value can be 
