164 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
(7) At one locality definite impregnations of the conglomerate by 
basic igneous material, perhaps melaphyr, have been observed. At 
two other localities there are less certain indications of a similar char- 
acter: 
THE NARRAGANSETT BASIN SERIES.— Arkose. No specimens of 
arkose from the Narragansett Basin have been seen by the writer. 
The rock as described by Foerste is more decomposed than that of 
either the Boston or the Norfolk Basins. It now consists of detrital 
quartz from decayed granite with interbedded clay. The quartz 
grains are not well rounded. (Foerste, b, p. 269.) 
Conglomerate: — Matrix. The materials of the matrix are appar- 
ently much the same in the Narragansett as in the Boston and the | 
Norfolk Basins. The main constituents are quartz, feldspar, and ' | 
felsite. Some specimens, however, contain more argillaceous and 
carbonaceous materials. Perhaps the most striking difference in the 
constituents of the matrices of the rocks in the three basins is the 
abundant occurrence of white mica in the Narragansett Basin and 
its absence in the others. The size, shape, and arrangement of the 
grains is similar to the corresponding features of the Norfolk Basin. 
——:— Pebbles. Among the pebbles of the Narragansett Basin con- 
glomerates the same general types of rock occur as in the other regions. 
Quartzite, felsite, and granite are the principal substances represented. 
There are, however, two important features of the pebbles that are 
not known to occur elsewhere in the regions under consideration: 
first, the appearance of Upper Cambrian fossils in pebbles of gray 
quartzite; second, numerous pebbles of muscovite granite. Although 
pebbles of gray quartzite of similar texture to those that contain the 
fossils are common in each of the basins, the fossiliferous pebbles are 
limited to the Narragansett Basin. A few such pebbles have been 
found within the basin but they are more numerous toward the south- 
ern margin, along the shore near Newport. In the drift at Martha’s 
Vineyard they are very abundant, and scattered pebbles have been 
picked up along the beaches south of Nantasket (Woodworth, d, p. 
109-113). The muscovite granite pebbles occur only in the Dighton 
Conglomerate, the upper member of the Narragansett series. They 
are abundant in the upper conglomerate at Attleboro. Pebbles of 
white quartz are abundant in some of the lower members of the 
Carboniferous series. 
The size of the pebbles is variable. In the lower members the peb- 
bles probably do not exceed three inches in diameter but in the 
