. The Earth beneath the sea : History . Fig. 1. Two kelp holdfasts {Macrocystis pyrifera) afloat in 25 m depth off Coronado Islands, Mexico. Largest is about 40 cm long and both consist of probable Middle Miocene sandstone and conglomerate. Note that intermittent touching of the bottom can produce holes and other markings on the sand. ( Navj^ photograph by R. F. Dill.) impressions. Most of the rocks are drifted inshore, as shown by the fact that beaches near kelp beds usually contain many rocks having remnants of hold- fasts and encrustations of calcareous red algae, bryozoans, rock oyster
. The Earth beneath the sea : History . Fig. 1. Two kelp holdfasts {Macrocystis pyrifera) afloat in 25 m depth off Coronado Islands, Mexico. Largest is about 40 cm long and both consist of probable Middle Miocene sandstone and conglomerate. Note that intermittent touching of the bottom can produce holes and other markings on the sand. ( Navj^ photograph by R. F. Dill.) impressions. Most of the rocks are drifted inshore, as shown by the fact that beaches near kelp beds usually contain many rocks having remnants of hold- fasts and encrustations of calcareous red algae, bryozoans, rock oysters, and other organisms which live below the low tide level (Emery and Tschudy, 1941), Single rocks rafted to beaches by kelp weigh as much as 10 kg, and one holdfast was found to contain an estimated 25,000 pebbles and granules coarser than one millimeter in diameter. Some plants also float seaward where masses of the larger ones have been
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectoceanbottom
