92 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
Generally the Soboruco or old reef rock occurs immediately at the 
water line, forming an abrupt undermining bluff from five to ten feet 
high (See Plate XXVIII). Im addition to the low level formation, two 
distinctly higher reefs are sometimes discernible, often a hundred yards 
or more back of the present beach line, at altitudes of 25 and 70 feet 
respectively, and constituting distinct formations. Owing to the fact 
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Fıgure 29. Relations of Elevated Reefs near Hopewell. 
60" 
that the old reefs of these three levels are conspicuous bench marks 
whereby the succession of other formations can be determined, we shall 
discuss them, where separable, under the names of the Coast Soboruco, 
Barbican, and Hopewell formations, respectively. Where not separable, 
or where their exact equivalence is indeterminate, the general term 
Soboruco will be used. Furthermore, while we believe the sequence of 
all the formations of the Coast Series is as given in the general table, 
page 42, for the purpose of discussing the reef made formations together, 
that order will be temporarily departed from and the latter will now be 
described. 
The best exposures! of the Soboruco observed by us were along the 
road following the coast of the east end of the north side of the island 
between Port Antonio and Northeast Point, but the sequence of the suc- 
shells, Foraminifera, etc. Microscopic examinations of fragments of limestone 
broken from coral reefs sometimes show no traces of coral structure. Coral, more- 
over, is more readily decomposed than shell, sand, or foraminiferal limestones.” — 
Nat. Sci., November, 1897, p. 290. 
“ Coral-reef Rock. — The rock forming the coral platform and other parts of the 
solid reef is a white limestone, made out of corals and shells. In some parts it 
contains embedded corals; in others, it is as compact as any Silurian limestone and 
without a fossil of any kind, unless an occasional shell. The compact non-fossil- 
iferous kinds are formed in the lagoons or sheltered channels; the kinds made of 
broken corals, on the seashore side, in the face of the waves; those made of corals 
standing as they grew, in sheltered waters, where the sea has free access. Large 
portions are a coral and shell conglomerate.” — Manual of Geology, by James D. 
Dana, Fourth Edition, New Haven, Conn., 1895, p. 140. 
1 The distribution of the Soboruco in Jamaica is well shown on the Geological 
Map aecompanying the Jamaican Reports, and in the text it is discussed under the 
head of the Coast Limestone. The text of the Reports gives only passing atten- 
tion to these rocks, and does not differentiate them into distinct formations. 
