Include: 

• Polychaeta - sand worms, tube worms 
• Oligochaeta - earthworms, Lumbricidae, Megascolecidae, Enchytraeidae

Lumbricid Earthworm (Class Oligochaeta)

1. Bilaterally symmetrical, segmented worms
2. Intestine complete and regionally specialized
3. Closed circulatory system
4. Nervous system well developed; dorsal cerebral ganglion, ventral nerve chord, circumenteric connectives
5. Excretory system usually metanephridia, sometimes protonephridia
6. Paired, segmentally arranged bundles of epidermal setae
7. Head consists of a presegmental prostomium and peristomium
8. Sexes separate or hermaphroditic
9. Marine, freshwater and terrestrial species

The functional biology of earthworms is an important component of the functioning of the soil foodweb.  They contribute to mineral and nutrient cycling, soil structure, aeration, porosity, and the fragmentation and redistribution of organic matter.

Enchytraeid (Class Oligochaeta)

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