The molluscs are one of the most diverse and abundant groups of animals in the world today. An understanding of the manner in which this group has diversified in form and habitat is hampered by the lack of information concerning the precise relationships and ancestry among the molluscan classes. The positions of the thirty- seven genes around the circular mitochondrial DNA molecule will be determined from representatives of the classes of molluscs and other animals believed to be related to molluscs on the basis of anatomical characters. These positions will be determined by DNA sequencing of selected regions of the mitochondrial molecule for each of the animals in the study. This data will be combined with DNA nucleotide sequencing of selected regions of the mitochondrial molecule for each of the animals in the study. This data will be combined with DNA nucleotide sequence data from several of the conserved protein-coding mitochondrial genes in order to understand precisely how these animals are related. This approach, using data from two different molecular levels, is appropriate when studying truly ancient radiations of animals. The results of this study will form the basis for the first clear analysis of trends in the form, diversity, and ecology of the molluscs.
