Mathematical models of shells enable researchers to estimate the maxim
um possible sizes of organisms that once occupied fossil shells. In th
is study, a whorl-by-whorl method of determining coiled shell volumes
and surface areas is introduced. The whorl-by-whorl analysis yielded r
esults that were more accurate than those obtained from a model that a
ssumes isometric growth, when both were used to calculate volumes of g
astropod shells. The whorl-by-whorl method is more laborious, but it i
s better suited for the analysis of shells exhibiting allometric varia
tion than are methods that use models of isometric growth.