Concept
Version 7
Created by Boundless
Classes of Echinoderms
Sea cucumbers
Sea cucumbers are the only echinoderms that demonstrate "functional" bilateral symmetry as adults, as they lie horizontally as opposed to the vertical axis of other echinoderms.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"Conspicuous Sea Cucumber, Coconut Island, Hawaii."
http://en.wikipedia.org/wiki/File:Conspicuous_Sea_Cucumber,_Coconut_Island,_Hawaii.JPG
Wikipedia
Public domain.