缓步纲

[ noun ]
in some classifications considered a separate phylum: microscopic arachnid-like invertebrates living in water or damp moss having 4 pairs of legs and instead of a mouth a pair of stylets or needlelike piercing organs connected with the pharynx
<noun.animal>

Tardigrada \Tar`di*gra"da\, n. pl. [NL. See {Tardigrade}, a.]
1. (Zo["o]l.) A tribe of edentates comprising the sloths.
They are noted for the slowness of their movements when on
the ground. See {Sloth}, 3.

2. (Zo["o]l.) An order of minute aquatic arachnids; -- called
also {bear animalcules}, {sloth animalcules}, and {water
bears}.