Crinoids: Sea Lilies, Feather Stars: Often misidentified as brittle stars or entirely overlooked as hidden or decorative ornaments due to their plant-like appearance, immobile/anchored sea lilies and the related, mobile feather stars make up the most ancient class of the phylum echinodermata, the Crinoidea (cry-noi-day-ah).

Due to easy breakage, suspension feeding habits and shy and retiring behavior these animals are considered challenging to keep. Most are doomed from difficulties accumulated from the time of their collection to delivery to your outlet. Feather stars need not be impossible however, as you will see.

Sea Stars: Completely marine echinoderms of obviously overall pentaramous symmetry. Live oral side down, feeding on a myriad of sedentary invertebrates and detritus, detrital infauna.

Brittle/Serpent and Basket Stars. The Brittle or Serpent Stars are grouped as the Class Ophiuroidea, characterized by having highly mobile arms that can be used to assist in (relatively) rapid motion. These starfish-like echinoderms are decidedly quicker and more delicate than asteroids. Their common name is derived from their sinuous, snake-like movements, and the fact that they're truly brittle and break away easily if they come under attack. The podia in this class are generally used as sensory organs, rather than for active feeding as with their kin, the asteroids. There are more than 2,000 described species worldwide, and they're found congregating throughout shallow reef environments, hiding under rocks and within and between other living organisms. 

Basket Stars:

One fast mention of the bizarre Basket Stars. Though some folks have reported reasonable success in their husbandry (see references below), these nocturnal animals are by no means easy to keep in captive conditions. They require specialized, large facilities, and diligence in their food preparation and administration.

Sea Urchins and Sand Dollars, Class Echinoidea: Friends and associates who know me to be an avid diver frequently ask whether I'm concerned with potential encounters with sharks, rays, giant squids and the like. My standard reply is that hour per hour spent the most dangerous activity we all engage in is driving on the freeway. In all honesty, in the way of moments spent underwater, other than your dive buddy, Sea Urchins are the most realistically harm/hurtful organisms.

Family Diadematidae: Astropyga, Diadema, Echinothrix.

Family Echinometridae: Colobocentrotus, Echinometra, Heterocentrotus.

Family Toxopneustidae: Lytechinus, Toxopneustes, Tripneustes.

Family Cicaridae:

Order Spatangoida: Heart Urchins

Order Clypeasteroida: Sand Dollars

Sea Cucumbers, Class Holothuroidea: With body shapes ranging from spherical to long and worm-like, bizarre rings of tentacles circling a non-descript head-end, these slow-moving, drab to brightly colored and marked invertebrates are well-known at least by sight, by most aquarists.

Genus Actinopyga: "Toothed Sea Cucumbers", named for the series of five teeth ringing their anus.

Genus Holothuria: 

To: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 13, Part 14, Part 15,