204 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
same strike a mile or more to the west and from the prevalence of slate 
drift along the beaches to the north. Professor Wolff, in a petro- 
graphic study of the melaphyr, describes the latter as a dike (p. 231). 
Professor Crosby, on the other hand, from the unsymmetrical section 
presented by the melaphyr and from differences in the character of 
the conglomerate on the north and south of the melaphyr, believes 
the latter to be a flow (n, p. 494), which, together with the inclosing 
sediments, is now inclined southward and forms part of the southern 
limb of a faulted anticline that extends westward to the granite border 
and connects westward with the conglomerate already noted near 
President’s Hill (ibid., p. 498). On account of the absence of con- 
glomerate outcrops between Rock Island and the granite boundary, 
and the somewhat doubtful character of the conglomerate near Presi- 
dent’s Hill, the conglomerate area has not been extended in that direc- 
tion on the map (Plate 7). 
South of the supposed Hough’s Neck anticline slate again appears 
which is apparently similar to that immediately north, with which it 
seems to merge eastward and also westward, though in the latter 
direction it may be interrupted by the supposed anticline. ‘The age 
and stratigraphic position of this whole area of slate south of the 
Hyde Park-Squantum anticline is somewhat doubtful. If the slates 
are Carboniferous they are doubtless conformable with the conglom- 
erates and overlie them. So far as the evidence of superposition of 
strata may be observed in the field it is favorable to this view. 
These slates, however, bear a close lithological resemblance to those 
of the Somerville area and the same obscure, possibly organic, impres- 
sions observed in the Somerville slates are found in the slates near 
the Norfolk Downs station at Wollaston (Woodworth, a, p. 126). 
Tf the Somerville slates are considered as Cambrian it would seem 
that the Neponset slates should also be so considered. Evidence in 
favor of this view is not entirely wanting. Around the eastern end 
of the Blue Hill Range the lowland is continuous from the region of 
the Neponset slate to the localities at Weymouth and Braintree, where 
known Cambrian fossils have been found. Slate patches or outliers, 
cut by granite dikelets, rest on the granite at Quincy (Crosby, n, P- 
428 et seq.). Areas of slate near the Boston and Hyde Park boundary 
in the eastern part of the Stony Brook Reservation and the immediately 
contiguous territory show igneous contacts with fine granite and quartZ 
porphyry, irregular dikes or apophyses of quartz porphyry and more 
regular dikes of normal felsite (Crosby, p, p. 41-42). These igneous 
rocks are known to be Post-middle Cambrian because of their relations 
