112 The American Geologist. hcbruai .899 
have many examples of these remains as metamorphism as 
been sufficiently severe as a rule to destroy almost every ti\ ce 
of a former life, excepting the semi-stratified arrangement of 
the silica presumably due to worm action. 
These are the oldest remains yet described from Massa- 
chusetts. The stratigraphical determinations upon which the 
age of these remains is based are as follows: a greater degree 
of metamorphism, of the regional kind (a criterion of proved 
value), compared with the Cambrian to the east, the region 
chosen for special study being clearly older than the sedi- 
ments of the Boston Basin series, the two being found in close 
proximity yet showing divergence in dip and strike. Second- 
ly, there are at least three systems of dikes found in the older 
Algonkian series not found in the Boston Basin series. A 
fourth system of dikes although relatively scarce is found to 
an equal evtent in both areas. The evidense in this case is, 
I think, small but reliable. The difficulty has been that the 
dike materials are so nearly alike in the different systems that 
it is difficult to separate them lithologically to advantage, but 
by supplementing this evidence with the habit of occurrence, 
a sequence is obtainable. The three older systems have diflfer- 
ent directions from the fourth, showing a possible change in 
the stress, the diking being dependent upon faulting; this 
would require a lapse of time. The presence of newer sys- 
tems of dikes in the Basin series, probably derived from a center 
of disturbance to the east of the present coast line, makes the 
dike evidence exceedingly complex. The results of the writ- 
er's studies are that every system of dikes in the basin has, or 
would have, if the disturbance had penetrated far enough, its 
counterpart in the area here described while the reverse is 
not true. The number of dikes, excluding local multiplica- 
tions, may also be considered. The great number in the older 
group has given rise to the mistaken idea that the whole of a 
belt which would include the Stonybrook and Kendal (ireen 
members was diorite. It is needless to say that such a mis- 
take would never be made in the basin; that series is comj^ara- 
tively unaltered. The transition is accomplished to the ob- 
server by stepping across a fault line. It is evident to the 
experienced eye that the Basin series has been deposited on 
the eroded surface of the older series. A third ground for 
