Main characteristics of Annelida:

(i) They are triploblastic, bilaterally symmetrical, coelomate, soft and elongated animals.

(ii) Their body is metamerically segmented externally by transverse grooves and internally by septa.

(iii) They have a tube-like alimentary canal, which is complete and extends straight from mouth to anus.

(iv) Reproduction is sexual. Sexes may be separate or united (hermaphrodite).

Examples: Sea mouse, earthworm etc.