96 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Microscopical. No. 800. Figure 7.—A dolomitic limestone in 
which the matrix consists of crystals of dolomite. Most of the organ- 
isms are coated with minute acute crystals, probably calcite. The 
echinid spinés and some of the sections of Amphistegina appear almost 
unaltered, but many of the organisms have partially recrystallized, and 
rhombs of dolomite have invaded the organisms from without inwards. 
This is well seen in several longitudinal and transverse sections of 
Lithothamnion, while a Halimeda has some of its tubules unaltered, 
but in others rhombs of dolomite have been formed, and destroyed 
the boundary of the walls of the tubules. A cavity in the rock has 
been filled with clear crystals of dolomite, while zoning by included 
muddy material is well seen in those crystals formed by the recrys- 
tallization of Lithothamnion. 
No. 811. A dolomitic limestone, with a fair quantity of semi-opaque 
material. Much of the slide, however, consists of rhombohedra of dolo- 
mite, with dark centers parallel to the outside boundary, and represent- 
ing “silt” caught up during recrystallization. Cavities are numerous, 
and the walls of these are lined with clear crystals of dolomite. 
East Coast. — One specimen has been analyzed from the summit of 
the upper cliff on the East Coast at a height of 800 feet. 
Chemical. — It is a limestone containing only 2.44 per cent of mag- 
nesium carbonate and .15 per cent of calcium phosphate. 
Calcium Magnesium Calcium 
Number. Height. Carbonate. Carbonate. Phosphate. 
134 800! 97.66 2.44 15 
Microscopical. No. 134. — This is a limestone containing many sec- 
tions of Polytrema planum, while Lithothamnion also occurs. Semi- 
opaque material is present in the matrix, while clear calcite fills some 
of the cavities. 
Second Inland. Cliffs (Older fringing Reefs — Lower Pliocene ?). 
SouTHEAsT OF PHospHATE Hii. — This is one of the fringing reefs 
which partly mask the older rocks in this section. It occurs between 
the levels of 600 and 300 feet. 
Chemical. — No. 617 occurs on the subhorizontal flat marking the top 
of the reef or cliff, and contains 34.1 per cent of magnesium carbonate. 
No. 618 was found at the outer edge of the flat at the top of the cliff, 
and on analysis yields no less than 43.30 per cent of magnesium car- 
bonate. This is the most highly dolomitized of any of the limestones 
