Historical reference: Do not rely on this information. It is very old. About this collection
Arthropoda, the phylum (or division of the animal kingdom) which includes all animals with hollow-jointed appendages. The body is normally composed of a series of segments, usually more or less dissimilar, protected by a hard external skin The phylum includes five classes, Pycnogonida. Crustacea, Arachnida, Protracheata, Myriapoda, and Insecta.