GENERAL HISTOLOGY

Detailed explanation-1: -Answer and Explanation: The only animal in this list that does not belong to the echinoderm phylum is B) sea squirt.

Detailed explanation-2: -Examples of echinoderms include sea stars, sea urchins, sea cucumbers, brittle stars, and feather stars (Fig. 3.83). Although they may appear very different, echinoderms all have two major defining characteristics that set them apart from all other animals: a water vascular system and five-sided radial symmetry.

Detailed explanation-3: -Hence from the above detail of echinoderms we can say that the crayfish are not associated with the echinoderms.

Detailed explanation-4: -Complete answer: Option A Sea urchin: Sea urchins are generally spiny, spherical, echinoderms of the class Echinoidea. Sea urchins move slowly, crawling on tubular legs and sometimes pushing each other with their spines. Sea urchins do not belong to the class Crinoidea.