PLATE LV. 
OOLITES AND BASALT FROM SHAN-TUNG. 
A. Girvanella (?) tubes in oolite. This shows an oolitic body with the usual concentric and 
radial structures inclosing an elongate bundle of tubules which have been described 
as alge and given the name Girvanella. (Red oolite from the Lower Cambrian near 
Ch’ang-hia, Shan-tung. Specimen 10, ordinary light, x 70, page 379.) 
B. An oolitic body which does not show the usual concentric or radial structures. The 
light spots are calcite, while the dark part is amorphous hematite. It is thought that 
the granular texture of this section has been caused by the crystallization of the car- 
bonate and that during the process the ferruginous impurities were relegated to the 
boundaries between the calcite grains, thus destroying the original concentric structure 
and developing in its place a net-work of hematite. The matrix in which the bodies 
are embedded consists of calcite darkened with earthy iron ores and containing a 
few small flakes of mica. (Same as last, ordinary light, x 50, page 379.) 
C. Slightly altered oolite. The dark circular sections of oolitic bodiesshow minutely crys- 
talline calcite darkened by finely divided carbonaceous matter. They are surrounded 
by radiate fringes of calcite and are embedded in a clear granular matrix of the same 
mineral. The advance of crystallization has sufficed only to obscure the nuclei and to 
dim the concentric banding. Compare with Plates LIV, E and F, and LV, D and E, 
for less altered and more altered phases. (Black oolitic limestone from the Cambrian 
near Ta-miau-ssi, Ssi-ch’uan. Specimen 143, ordinary light, x 20, page 470.) 
D. Granular oolite. This section represents a stage intermediate between that depicted 
inCand E. The calcite of both matrix and corpuscles is rather coarsely crystalline. 
The nuclei of the oolitic bodies are entirely obsolete, but a trace of the concentric 
banding is still preserved by the circular streaks of dark impurities which pass indis- 
criminately through the more recently formed crystals of the carbonate. The slide 
shows the peculiar oblong shape and rude tangential orientation of many of the cal- 
cite crystals. (Black and gray oolite typical of the Ch’ang-hia formation near the 
village of that name, Shan-tung. Specimen 18, ordinary light, x 48, page 381.) 
E. Crystallized oolite. The dull ground-mass consists of fine-grained calcite, as in ordi- 
nary limestone. The round bodies are oolitic nodules which have completely crystal- 
lized. The parallel cleavage serves to show that several of them consist of a single 
crystal, which, however, retains the outline of the original nodule. This figure should 
be compared with preceding sections. In the present slide the traces of concentric 
structure are obliterated. (Oolitic limestone from the Middle Cambrian near Ch’ang- 
hia, Shan-tung. Specimen 11, slide (a), ordinary light, x 20, page 382.) 
F. Porphyritic basalt. The dark ground-mass is composed of feldspar, augite, and iron 
ores, in particles of all shapes and sizes. The crystals bordered with black near the 
center of the field are olivine partly altered to serpentine. Just above this and to 
the left there is a basal section of pyroxene. The clear phenocrysts are labradorite. 
In the largest of these, minute inclusions are arranged in a zone parallel to the outline 
of the crystal. (Basalt from Post-Carboniferous strata near Yen-chuang, Shan-tung. 
Specimen 54, polarized light, x 50, page 407.) 
