J. D. Dana’s Mineralogical Contributions. 215 
much. But excepting Wagnerite, the relations between the axes 
are close. In Wagnerite the plane w (see Brooke and Miller) is 
taken as the basal plane O. ~ A 
In Triphyline 1:1 = 94°; but the approximation to the others 
in the value of the vertical axis is not very close, even if the 
prism be oblique. ‘The author has before shown that Crocoisite 
is homceeomorphous with monazite. 
he Monazite and Apatite series are mutually dimorphous. 
13. Datholite and Euclase. 
The following figures of crystals of Datholite present some 
planes hitherto unobserved. Fi 1. 
land 2 are from Roaring Brook, 
Connecticut, and 3 and 4 from . 
Isle Royale, Lake Superior. 
Fig. 2 presents only a lateral por- 
tion of a crystal which in most 
respects resembles figure 1. A 
tratisparent crystal from this lo- 
tality afforded for I : I, 115° 12’ 
giving by calculation 73:73 76° 
8’. The plane O and all the 
others are highly polished, ex- 
Cepting sometimes 82, 72, and usually s; s replaces 
edge I: 23; and as its intersections with 63 and 4 are 
not parallel, nor is the intersection with 63 parallel to_ . 
that of 63 and 6%, it is probable the plane is 'y - }. 
The angles of 188 are X= 139° 25, Y=57° 8, 
Z=141° 32. The minute plane ¢, figure 4, gives 
4. 4. 
®pproximately © : ¢ = 140°—142°, é@: ¢= 109° 30’, whence 
*t=1419, which are near the angles of plane 22; but the inter- 
Sections of ¢ with 2 and 2% are not parallel, although those with 
and 43 are parallel. From the last parallelism m =4n-—(2 +2). 
