Cetacea and two (external) limbs that are modified into flippers. Though not as flexible or agile as seals, cetaceans can swim very quickly, with the killer whale able to travel at in short bursts and the fin whale able to cruise at . Dolphins are able to make very tight turns while swimming at high speeds. The hindlimbs of cetaceans are internal, and are thought to be vestigial. Baleen whales have short hairs on their mouth, unlike the toothed whales. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water, and baleen whales have a tactile system
Flat-spired three-toothed snail among 40 species of tridopsine snails in eastern North America. Populations were divided into family trees showing the phylogenetic relationships among 18 groups of species. Nine of these groups consisted of a single species, of which "Triodopsis platysayoides" was one group. This species of snail is endemic to the United States. The flat-spired three-toothed snail is found only in West Virginia, among Upper Connoquenessing sandstone outcroppings and boulders, in a restricted area along the rim of the Cheat River gorge. The U.S. Fish and Wildlife Service considers this snail to be threatened since 1978. Little is known about the life