. Bulletins of American paleontology. or entirely of minute but fully formed shellswhose origin has long been a paleontologic puzzle. Postmortem Shell MovementWhen I originally undertook this study I hoped thatdeveloping an adequate body of quantitative datawould permit reconstruction of the details of the orig-inal living fauna. As part of this inquiry, my assistantsand I for many years kept counts of the number ofright and left valves of clams. In the end, my hope ofdescribing the living fauna from the shells aloneproved illusory, but the valve counts provide interest-ing information on the
. Bulletins of American paleontology. or entirely of minute but fully formed shellswhose origin has long been a paleontologic puzzle. Postmortem Shell MovementWhen I originally undertook this study I hoped thatdeveloping an adequate body of quantitative datawould permit reconstruction of the details of the orig-inal living fauna. As part of this inquiry, my assistantsand I for many years kept counts of the number ofright and left valves of clams. In the end, my hope ofdescribing the living fauna from the shells aloneproved illusory, but the valve counts provide interest-ing information on the amount of sorting that takesplace among dead shells. The details of this study canbe found in Appendix 3. To summarize the data, the numbers of right andleft valves recovered from any free-living ( unat-tached) pelecypod were not found to be statisticallydifferent when we had counted an adequate number ofspecimens. This suggests strongly that, after death, thevalves of each pelecypod tend to remain essentially in 40 JULLETIN 370. -ligLire 3y.—Dr. Kenneth W. Cniaeks p place, subject only to the minor movement caused bybottom dwelling scavengers and to local movementsof the bottom of the water column. Two factors that can cause disparate valve countsappear to be: (1) Pelecypods in vviiich one valve is cemented orotherwise attached to a substratum. Such pelecypodsare normally represented only by the free valve. (2) Pelecypods in which the crystalline structure ofone valve is significantly more fragile than in the op-posite valve tend to be unequally represented. Theprincipal example of this is Piiutadci. in which theright valve is weaker. The conclusion that there has been little post-mor-tem transportation of pelecypod shells leads directly tothe next topic: How far do storms transport shells? Storm of She-llsMovement of shells by storms has long been a mat-ter of debate within the paleontologic community. Onone hand, there are those who feel that such movement
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