There are four classes of Arthropods:

Chelicerates, such as spiders, mites, ticks, scorpions, horseshoe crabs
Trilobites (extinct)
Crustaceans, such as lobsters, crabs, and shrimp
Uniramians, such as millipedes, centipedes, and insects

Flat Millepede and eggs – Gosodesmus claremontus | Deer Park to Phoenix Lake | March
Flat Millepede and eggs – Gosodesmus claremontus | Deer Park to Phoenix Lake | March
Yellow-spotted Millipede – Harpaphe haydeniana | Palomarin Trail | May