100 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Chemical. —- Two analyses only have been made. Both the rocks are 
limestones, and contain 2.3 and 3.0 per cent of magnesium carbonate 
respectively. 
Calcium Magnesium Insoluble 
Number. Height. Carbonate. Carbonate. Residue. 
630 270’ 97.0 3.0 074 
631 220’ 97.7 2.3 
Microscopical. No. 630.-- A somewhat cavernous limestone, whose 
matrix consists of calcite. A fair number of rhombohedral crystals occur, 
some of which have dark centers. The organic fragments are small and 
badly preserved, and are represented by an interior of calcite with dirt 
lines round the external margins of the organisms. 
East Coast. — Steer Point. — The reef here makes a vertical cliff 
between the levels of 200 and 300 feet. 
Chemical. — All the rocks are limestones with magnesium carbonate in 
amounts varying from 2.2 to 6.7 per cent. 
SLES HEGRE | “Gaenonaie, || Catwonstay | teatdue, 
1010 300° 96.9 3.1 2 
1009 290’ 93.3 6.7 = 
1008 275’ 95.8 4.2 os 
1007 260’ 95.5 4.5 as 
1006 250’ 95.4 4.6 on 
1004 230 96.8 3.2 026 
1003 215’ 97.8 2.2 - 
1002 200’ 95.0 5.0 = 
1001 200’ 97.1 2.9 aH 
Microscopical. No. 1006.— A fragmental rock made up of pieces of 
older rocks containing fragments of corals and of Orbitoides. These frag- 
ments are cemented with a matrix first of fibrous calcite, the consolidation 
being completed with a granular mosaic of calcite crystals. 
No. 1005. <A limestone containing much opaque “mud,” in which 
casts of simple corals are preserved. Carpenteria is abundant in this 
rock, 
