Crayfish Family (Astacidae) is found primarily in North America, although a few species are found in Europe and Asia.

Lobsters and Crayfish (Decapoda/Astacidae Section) contains the American Lobster and the North American Crayfish.

Shrimps and Crabs (Order Decapoda) contains most of the larger freshwater and marine species of crabs, crayfish, shrimp, and lobsters. They have a total of ten pairs of legs, four of which are used for walking. The first pair of legs is often modified into pinchers used for eating and defense.

The following list is based on the division of the Decapoda into five different suborders based on adult shapes of the various life forms:

Natantia - Shrimp-like
Brachyura - Crab-like
Nomura - Hermit Crabs and relatives
Astacidae - Crayfish and Lobster-like
Palinura - Spiny Lobsters and Spanish Lobster

The sub-classification of the Order Decapoda is in a state of change. For a short summary of this situation, please refer to pages two and three of Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States by Austin Williams published by the Smithsonian Press, Washington, D.C., in l984. If one uses adult shape as a method of classification, one gets one organization, and if one uses larvae shape for classification, one gets a different organization.

Crustaceans (Class Crustacea) is a large class of mostly aquatic animals. Although many species are marine, there is a large number of small freshwater species and a few species of larger freshwater crayfish. There are many subdivisions to the Crustacea including such diverse animals as water fleas, fish lice, barnacles, crabs, shrimp, and crayfish. There are probably over 26,000 species in this class.

Jointed Legged Animals (Phylum Arthropoda) make up the largest phylum. There are probably more than one million different species of arthropods known to science. It is also the most successful animal phylum in terms of the total number of living organisms.

Butterflies, beetles, grasshoppers, various insects, spiders, and crabs are well-known arthropods.

The phylum is usually broken into the following five main classes:
Arachnida: - Spiders and Scorpions
Crustacea: - Crabs and Crayfish
Chilopoda: - Centipedes
Diplopoda: - Millipedes
Insecta: - Insects

There are several other "rare" classes in the arthropods that should be mentioned. A more formal list is as follows:

Sub Phylum Chelicerata
C. Arachnida: - Spiders and scorpions
C. Pycnogonida: - Sea spiders (500 species)
C. Merostomata: - Mostly fossil species

Sub Phylum Mandibulata
C. Crustacea: - Crabs and crayfish

Myriapod Group
C. Chilopoda: - Centipedes
C. Diplopoda: - Millipedes
C. Pauropoda: - Tiny millipede-like
C. Symphyla: - Garden centipedes

Insect Group
C. Insecta: - Insects

The above list does not include some extinct classes of Arthropods such as the Trilobites.

Animal Kingdom contains numerous organisms that feed on other animals or plants. Included in the animal kingdom are the lower marine invertebrates such as sponges and corals, the jointed legged animals such as insects and spiders, and the backboned animals such as fish, amphibians, reptiles, birds, and mammals.

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