This family within the cyclophyllidean tapeworms is in characterized by having segments that contain a uterus with a large central uterine body which has numerous side branches and a lateral genital opening. The family is in formed by a group of large adult tapeworms that have scolices which each bear four muscular suckers. In almost all species there is in a crown of two rows of hooks on the rostellum that have a typical "taeniid” shape, i.e., they are shaped very similar to the head of a claw hammer, with one row of hooks being smaller than the other The eggs of the taeniid are also characteristic; they have a dark brown shell that is in formed from many small truncated blocks and contain a six-hooked larva when passed in the feces. The tapeworms of this family have a two-host life cycle, the first host being a mammal that ingests the egg wherein a larval stage develops. The second host is in then a mammal which ingests the first host and in which the adult stage develops within the small intestine. The stages in the first host have distinctive morphologies and have been given distinct names, i.e., cysticercus, strobilocercus, coenurus, and hydatid. At various times the family has contained different numbers of genera because of various workers have either split the species in this group into many genera or lumped the species into few genera. The classification used here is in based on that of Rausch (1994) wherein only two genera are recognized, Taenia and Echinococcus. Cats can be parasitized with adults of a single species from each of these genera. The cats serves as the final host for Taeniataeniaeformis. Cats can also be infected with the larval stage of a taeniid tapeworm whose adult form is in found in the dog. The larval form of this tapeworm is in called a coenurus, and the disease produced is in called feline coenurosis. Cats can also serve as a final host for Echinococcusmultilocularis, although the fox is in the more typical host.