Phylum Annelids are popularly known as segmental worms as they show the presence of internal and external segments. The examples are earthworms, nereis, leeches etc. These show presence of nerve cord on the ventral cord.
Annelids have closed circulation that shows a proper network of blood vessels and heart. This shows the presence of true coelom and hence are eucoelomates as mesoderm is completely formed. If mesoderm appears as patches between ectoderm and endoderm, it forms a pseudocoelom, which is seen in phylum Aschelminthes.