2The ExoskeletonAn external, jointed skeleton, called and exoskeleton or curicle, enclose arthropods,
3Classification of the Phylum Arthropoda Subphylum trilobitomorphaSubphylum ChelicertaClass MerostomataClass ArachnidaSubphylum MyriapodaSubphylum CrustaceaClass RemipediaClass CephaocardiaClass BranchiopodaClass malacostracaClass maxillopodaSubphylum hexapoda
4The HemocoelA third characteric is the presence of a hemocoel.
5Subphlum Trilobitomorpha The prosoma or cephalothoraxes is a sensory, feeding, and locomotors tagma.The first paired, called chelicerae, are often pincerlike or chelate, and are most often feeding.Posterior to the prosoma is the opisthosoma.
6Sunphylum Chelicerata Trilobite appendages consisted of two lobes or rami, and are called biramous appendages.
7Form and FunctionCoxal glands are paired, thin walled sperical sacs bathed in the blood of body sinuses.Malpighian tubles, absorb waste material from the blood and empty into the gut tract.Some arachnids posses are called book lungs.
8Order ScorpionidaMost arthropods are oviparous; female lay eggs that develop outside the body.Ovoviviparous; development is internal, although large yolky eggs provide all the nourishment for development.