MUSEUM OF COMPARATIVE ZOOLOGY. £13 
with scoriz at contact with upper sheet. No local close-grained texture 
at upper contact. 
Upper sheet dense as far as exposed in quarry ; becomes somewhat 
fine-textured at contact with lower sheet ; its original upper surface not 
seen in the quarry, but half a mile northeastward on the east side of the 
ridge, locality 19! (Fig. 6), the trap becomes vesicular. Several lines of 
fault breccia traverse the quarry, consisting of large and small angular 
fragments of trap contained in apparently unstratified sandstone ; often 
slickensided ; the trend of these breccias agrees with that of the neigh- 
boring faults, as determined by stratigraphic evidence. See special. 
account. 
No other significant exposures of the main sheet have yet been found 
in its further northward extension in Connecticut. 
Division III. Posterior RipGEs. 
Locality 20. Section numbers, 34-37, 74, 75. First ridge posterior to Saltonstall 
Mountain. Percival’s Report, p. 324. Percival’s notation, P. 1, E. I. 
The upper surface of this posterior ridge is exposed only near its 
northeastern end, at a road crossing, about a mile northeast of Salston- 
stall Pond (Fig. 11). Elsewhere the outcrops are generally dense, but 
sometimes vesicular on the back of the ridge. 
Upper portion of sheet very vesicular and glassy ; not locally close- 
grained at junction with overlying sandstone; sand grains and trap 
fragments occur together at upper contact ; sand fills vesicles in trap ; 
occasional water-worn fragments of trap in the sandstone a foot or more 
above the sheet ; base of sheet sub-amygdaloidal. 
Ridges of very coarse trap conglomerate occur in the neighborhood, 
but their relation to this sheet is not yet clearly made out. 
Locality 21. Section. number, 18-28, 187-193. Second ridge posterior to Saltonstall 
Mountain. Percival’s Report, p. 325. Percival’s notation, P. 2, E. I. 
According to our interpretation of the stratigraphy, this ridge is a 
second outcrop of the sheet already seen in the first posterior, here 
showing a western dip, as if on the eastern side of a synclinal ; its base 
is open in several small abandoned quarries near a road crossing, half a 
mile northwest of Branford station, Shore Line Railroad, locality 21 
(Fig. 11) ; and its upper surface, with something of the overlying sand- 
stone, is seen an eighth of a mile north of these quarries, on the eastern 
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