THE PETROGRAPHICAL PROVINCE OF ESSEX COUNTY 805 
are either extremely poor in, or quite wanting in, nepheline. 
These are true syenitic rocks and among my specimens two main 
varieties may be distinguished. They shade into the preceding 
group by imperceptible gradations. 
The first is found at a quarry on the north shore of Salem 
Neck, west of the Fort, and is essentially a border facies near 
the contact with essexite, which crops out close by on the other 
side of a small hollow. This is typically foyaitic (trachytic) in 
structure and shows the tabular feldspars and their parallel 
arrangement. A variety of this, met with farther east near the 
water’s edge, is brownish and porphyritic through the presence 
of abundant feldspar tables strewn irregularly in a feldspathic 
groundmass. These syenites resemble the foyaites in all essen- 
tials, except that nepheline is absent and the feldspars are nearly 
always microperthitic. The colored minerals are olive-green 
hornblende, brown biotite, and green aegirite, all in about the 
same amount. Magnetite grains and an occasional apatite needle 
are also found. 
This rock corresponds closely, both in evident structure and 
mineral composition, to the hedrumite of Brégger* from the 
laurdalite region, and which he defines as: ‘‘nepheline-poor to 
nepheline-free syenitic rocks with trachytic structure exactly cor- 
responding to that of the foyaites.’’ Since, however, its analysis 
(1) shows that it is decidedly more acid than Brégger’s analysis 
of hedrumite, it would better be classed with the pulaskites. 
The other type of syenite forms coarse-grained masses and 
veins in the nepheline-syenite, and is best represented by a 
specimen from Salem Neck given me by Mr. Sears. This shows 
a coarse-grained mass of pearly, tabular, alkali-feldspar crystals, 
arranged in radiating groups, with a little aegirite, etc., in black 
grains and a minute amount of magnetite. Under the micro- 
scope the feldspar tables are seen to be microperthite, though 
kryptoperthite is also seen, as well as albite alone, showing fine 
and clear twinning lamelle. There is possibly a slight admix- 
™BrROGGER, Zeit. Kryst, Vol. XVI, p. 40, 1890. It is more fully described later in 
Erupt. gest. d. Krist. geb., Vol. III, pp. 183 ff., 1897. 
