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PACIFIC SCIENCE, VoL XVII, January 1963 
Fig. 11. Top: Direction of littoral transport and sample locations along the Mana Coastal Plain. Note 
beach rock outcrops, and position of multiple beach ridges and recent and ancient dunes. 
Bottom: Variation in carbonate content and median grain size with distance along the Mana shoreline. 
Median diameters determined by Emery settling tube. 
erostegina. The remaining 45% was magnesium- 
poor calcite and presumably is derived from 
Amphistegina. Very little is known of the living 
depth range of either species. The highly worn 
appearance of all of the tests suggest that on 
Kauai they do not live on the reef but have been 
transported some distance. 7 
MANA COAST — LEEWARD BEACHES 
The Mana Coastal Plain (Fig. 11) consists of 
calcareous beach, dune, and lagoon sediments, 
mainly of marine biogenous origin, but includ- 
ing some terrigenous sands near the Waimea 
7 Ruth Todd, U. S. Geological Survey, suggests that 
both species may thrive in water down to at least 200 
ft (personal communication) . 
River. Well borings show that these marine sed- 
iments are about 125 ft thick near the base of 
the Puu Ka Pele slope, and may be 400-500 ft 
thick at the seaward edge of the Mana Coastal 
Plain. They lie on a gently sloping bench, ap- 
parently cut by waves into the original dome 
surface during a lower stand of sea level (Fig. 
The region west of the Waimea River, con- 
sisting of the Mana Coastal Plain and the Puu 
Ka Pele slope, is practically a rainshadow desert. 
This region receives an average annual rainfall 
of 18 inches (Table 1), the lowest rainfall of 
any major drainage area on the island. The lee 
coast has few fringing reefs, and those that do 
occur are more poorly developed than the reefs 
on the exposed windward coast. 
