114 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
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islands along the coast at variable distances from the shore rise to 
nearly this height and about Sao Francisco Bay well in back of the 
town there are low foot hills separated by valleys from the base of the 
Serra and from each other, and similar hills confront the somewhat 
higher ones at the south side of the entrance. Presumably this 
avaan 
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. Fie. 33.— Terrace about islet in the sea north of Laguna, Sta. Catharina. 
dissected rock bench is of very ancient date, early Pleistocene or 
Tertiary. 
A more recent set of rock benches form narrow platforms about 
many rock islands along this same extent of coast apparently standing 
from eight to ten feet above sea-level. They agree closely in level 
with the alluvial plains bordering the bays. Figure 33 gives the out- 
line of such a terrace skirting the base of a small rocky islet north of 
Laguna as seen from a steamer. Hartt (1870) has given abundant 
evidence of a recent uplift of the coast to this height. This change 
of level is seemingly very recent. 
Between the first described signs of a very ancient bench, and this 
recent uplift must be interpolated an episode of subsidence carrying 
the sea into the valleys at the base of the Serra do Mar. The harbors, 
great and small, are due to this change of level. The filling up of the 
harbors and river channels and the building of an underwater deposit 
makes an estimate of the depth of this depression too small but as the 
harbor at Rio de Janeiro has a maximum depth of 30 M. (Hartt, 
1870, p. 7) the sinking must have been equal to this depth plus the 
amount of the recent elevation. 
On the flats east of Paranagua there is a well-defined low beach 
ridge covered with dead shells of Ostrea and a smaller gibbous lamelli- 
branch at an elevation of eight or ten feet above sea-level and separated 
from the shore of the bay by two flats at slightly different levels. 
The shells are not worn; some of them have both valves in position. 
The situation of the deposit and the mode of occurrence of the shells 
is very different from that of the accumulation of shells left by 
aborigines on neighboring sandy deposits. 
Geographic Control of Human Occupation.— The effect of the several 
geographic features above outlined on the human occupation of 
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