574 The American Naturalist. [June, 
closely related to eschynife, with which it forms a group distinct from 
all other natural mineralogical groups. When placed in a position 
corresponding to the usual one for zschynite its axial ratio becomes 
a : b : c—.4681 : 1: .7192. Measurements of the best ar/vedsonite 
erystals gave .5496: 1: .2975 as the axial ratio for this species, with 
f=75° 4414’. The analysis of a large crystal ec (after treating 
with acid to dissolve magnetite) : 
SO ALO PeO, MoO MO MMO KO HO 
49.90 2.62 32.99 .05 .57 12.88 .IO 1.07 
Pterolite is regarded as an alteration product of barkevikite, con- 
sisting of a mixture of lepidomelane and egerine, and anigmatite is 
thought to be identical with cossyrite. An optical examination of 
hatapleite okay it to be monoclinic with æ : 6 : e—=1.7329: I: 1.3618 
and S=89° 4814’, and not hexagonal as formerly ja pposed, although 
it assumes the hexagonal symmetry when heated to 140°. Two varie- 
ties of the mineral are recognized. The first is a yellow variety to 
which the name katapleite is assigned, and the second a blue variety 
which is called soda-katapleite. The composition of the varieties is 
given as follows : 
SIO, 290, ALO, : EO CeO: NaO HO 
L : gs6 Ess Lr Bat gy 9.38 
II 44.04 30.94 .10 87 14.94 9.24 
Tritonite, according to Brégger, does not crystallize in the regular 
system, but is probably rhombohedral and hemimorphic. In this case 
& :c— 1: 1.114. The analyses that have been published as those of 
Erdmannite are thought to be analyses of a mixture of a melanocerite 
mineral with a member of the homilite group. Zukotite-Htanite is a 
deep brown variety of sphene, with most of the optical and crystallo- 
graphic properties of this mineral, but differing from it slightly in 
composition, which is as follows: 
SiO, ZrO, TiO, CeO, Ce,O, Y,O, CaO FeO MgO Na,O K,O Loss 
30.22 .18 34,78 2.57 -59 24.38 3.84 .50 .86 .27 ..31 
The soda-orthoclase of Fredriksvarn turns out upon close examina- 
tion to be an intergrowth of such fine lamellz of albite and orthoclase, 
that upon examination with low powers of the microscope, a section 
of this mineral behaves as if monoclinic. Brégger calls it cryptoperthite. 
Eudidymite has been carefully examined and its properties well estab- 
lished. It is a monoclinic mineral, ae in appearance heulan- 
dite. Its axial ratio is @: 4 : c=1.7107 : 1 : 1.1071, and P=86° 14’ 
. 
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