The pioneering work of David Raup introduced the use of computers to the science of paleontology in the early 1960s. Higher values mean opening of the shell becomes wider with each rotation. D affects the distance of the center of the tube from the axis of coiling. Higher values mean tube of the shell forms further from the coiling axis. T affects the distance of the center of the tube from the previous rotation along the axis of rotation.
Higher values mean the shell is taller.
Once you've made your selections from the sliders, click the Draw button or click the image of the shell to redraw the image. To more clearly see how the different parameters afftect the shell's shape, change one parameter, click Draw , and look for the differences. References Raup, D.M., 1962. Computer as aid in describing form in gastropod shells. McGhee, G.R., Jr., 1991.