No abstract

No abstract

No abstract

grown at a single temperature over the 24-hr period of these experimcnts, probably because of the discontinuous nature of the calcification process. Palcotemperature and paleosalinity determinations, such as by oxygen isotopic composition, of the total M. edulis skeleton would yield results higher than the mean temperature and salinity for the growth locality.Measuring growth in fossil M. eduh shells might be used to determine paleotemperatures and paleosalinities. Determining the number of days in a year in the geologic past on the basis of molluscan skeletal structure is probably not possible.

The relative abundance of suspension‐ and deposit‐feeding organisms in fossil communities has been used to interpret water turbulence in ancient environments. Trophic analysis of modern molluscan communities of San Francisco Bay and of Pliocene macroinvertebrate communities of the Kettleman Hills, California, suggests that the method is only partly valid for inshore environments, which may be more complex than those previously studied. Factors other than water turbulence must explain some differences in trophic proportions. Epifaunal communities consist largely of suspension‐feeding organisms regardless of other environmental factors, and relict sediments or sediments out of equilibrium with the normal hydrologic conditions in the area may lead to erroneous interpretations. Analysis of the total benthic macroinvertebrate communities of the southern California shelf indicates that the trophic proportions of the potentially fossilizable part of each community are not the same as the total community and is not always diagnostic of the environment.