Rhabditida

Rhabditida is an order of free-living microbivorous nematodes (roundworms) living in soil.

Genera include:

Rhabditis,
Caenorhabditis of which C. elegans is the nematode that has had its full genome deciphered,
Cruznema,
Pelodera,
Bursilla (Mesorhabditis),
Steinernema,
Heterorhabditis.