142 



Life 



Figure 124. Some important inhabitants of marshes in southern California: A, Zostera marina L., eel grass (x0.05); 

 B, Spartina leiantha Benth. (x0.05); C, Salicomia pacifica Standi. ( x0.05); D, Suaeda californica Wats. ( x0.05); E, Dis- 

 tichlis spicata (Torr.) ( x0.05); F, Cehthidea californica (Haldeman), horn shell ( xO.5); G, Macoma nasuta (Conrad), bent- 

 nose clam (x 0.8); H, Tagelus californianus (Conrad), jackknife clam (x 0.5). 



by some workers that bays and marshes 

 formed the route by which animals left the 

 sea to populate the land during the geologi- 

 cal past (Pearse, 1936). 



Marsh deposits are probably present in 

 the geological column but cannot often be 

 recognized through fauna alone because of 

 nearly complete solution of shells composed 

 of calcium carbonate. Some black shales 

 that have chitinous fossils (graptolites and 

 crab carapaces and claws) but few calcareous 

 fossils may well have been ancient marshes. 

 In some of them minor sedimentary struc- 

 tures (thin interrupted bedding and some 

 ripple marks) and organic structures (trails, 

 burrows, and faecal pellets — Hantzschel, 

 1955) support the interpretation of marsh or 

 mud flat deposits. Among the best-known 



black shales of this general type are those of 

 Paleozoic age in the eastern United States 

 and Europe (Twenhofel, 1932, p. 395). 



Sand Beaches 



Sand beaches form a more rigorous en- 

 vironment than the marshes owing to im- 

 pact and continuous reworking by wave 

 action. Because of the shifting substrate 

 large plants cannot become established ex- 

 cept high above the reach of waves. Micro- 

 scopic blue-green algae, however, sometimes 

 form a film covering the sand grains between 

 high tides and serving as food for grazing 

 Foraminifera (Reiter, 1957) and probably 

 for other small animals. The main food 

 supply for beaches is that of kelp and other 



