The Echo . echo16196873west Year: constant. This observation is based on hundreds of specimens from many different localities. This seemingly insignificant difference has proved invaluable in the course of field work in southern Florida where the geological sequence from upper Mio- cene through Pleistocene is decipherable solely on faunal bases, C. floridanus is upper Miocene and Pliocene in age and C. dilec- tus is Pleistocene and Recent; the presence of one specimen of either species is sufficient to determine the age of the beds. If these two forms were found together the small degree of
The Echo . echo16196873west Year: constant. This observation is based on hundreds of specimens from many different localities. This seemingly insignificant difference has proved invaluable in the course of field work in southern Florida where the geological sequence from upper Mio- cene through Pleistocene is decipherable solely on faunal bases, C. floridanus is upper Miocene and Pliocene in age and C. dilec- tus is Pleistocene and Recent; the presence of one specimen of either species is sufficient to determine the age of the beds. If these two forms were found together the small degree of difference between them would hardly be sufficient for the erec- tion of two distinct species; but as they are stratigraphically separated I feel no hesitation in using two specific names. Here many persons might use a subspecies designation. The use of such a designation is a subjective matter. Other than variation in the number of varices in certain groups, the species of Muricinae exhibit a remarkable morpho- logical consistency. The members of one species are constant in the development of the number and position of varical spines, although the strength of the spines may vary slightly. The num- ber of intervarical nodes is less fixed and frequently is a variable character. The overall shape of the shell in reference to the ratio of height to diameter is relatively invariable. Development of denticulation on either or both the inner or outer lips of the aperture is constant within a species and is a useful specific or even generic character. The shell ornamen- tation consists of spiral threads and axial protuberances which may be either varices or intervarical nodes, and, in addition, numerous small intervarical axial growth lines. The pattern formed by the combination of the axial and the spiral ornaimenta- tion is uniform within a species, usually varying only a minor amount. There are two basic types of protoconchs present in the Muricinae. I have named these the 'bulbous
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