63 JOURNAL OF THE 
coarsely fibrous or granophytic at the center and usually 
show between cross nicols an indefinite black cross. Occa- 
sionally also the concentric structure is well marked. The 
rays are too minute to permit of an accurate determination of 
their mineral composition by optical methods, but microchem- 
ical tests with hydrofluosilicic acid yield the small cubic crys- 
tals, characteristic of potassium fluosilicate as well as the 
hexagonal prisms of sodium fluosilicate. Judging from the 
greater abundance of prisms than cubes the fibrous feldspar 
is richer in sodium than potassium. ‘That feldspar, instead of 
chalcedony, is the most prominent constituent of the spheru- 
lites, is fully borne out also by its kaolinizing. under the in- 
fluence of the weather. 
The spherulites are embedded in a matrix composed chiefly 
of granular quartz. The grains are occasionally so large 
that the uniaxial positive character can be readily determined. 
Untwinned feldspar in small grains may be present in consid- 
erable amount but yet be easily overlooked. The quartzose 
character of the weathered matrix, however, shows that at 
least where most coarsely granular there cannot be much if 
any feldspar present in it. In places the matrix contains 
numerous minute parallel scales of what appears to be sericite. 
Associated with the most coarsely crystalline areas are a few 
scales of brown biotite and occasionally considerable green 
biotite, which in places is so abundant as to make quite prom- 
inent dark green spots. Both matrix and spherulites are 
traversed in a few cases by small veins of granular quartz, 
showing that there is a considerable amount of secondary 
quartz present. Both spherulites and matrix are rendered 
slightly microporphyritic by containing occasional crystals of 
plagioclase feldspar and quartz. The plagioclase, which, on 
account of its small angle of symmetric extinction, must be an 
acid one, in some cases forms the center from which the 
spherulitic fibres radiate. 
An isolated specimen of Paleotrochis was cut through the 
apices and found to be composed of granular quartz. The 
quartz was fine-grained upon the outside where the grains 
