ARACHNID A

a heterogeneous cla of the phylum Arthropod a, including spiders, mites, scorpions, king-crabs, and trilobites. The anterior segments are usually fused to form a cephalothorax, with six pairs of appendages, of which the first two are modified for seizing food, and the others contain excretory (coxal) glands. Many forms are provided with an internal plate-like skeleton, the endosternite. An elongated heart is found in the dorsal side of the abdomen. The sexes are separate, eons pag young generally resemble the adults.