630 APPENDIX B 



PHYLUM VIII. MOLLUSCA. The Mollusks. Bilaterally symmetrical or twisted. 

 Body enclosed in a shell (with rare exceptions). 

 Class 1. Chitons. (Amphineura.) 

 Class 2. Snails. (Gastropoda.) 

 Class 3. Tooth Shells. (Scaphopoda.) 



Class 4. Bivalve Molluscs. (Pelecypoda or Lamellibranchiata.) Clams, etc. 

 Class 5. Cephalopod Molluscs. (Cephalopoda.) Squids, octopus, etc. 



(Body segmented = metameric) 

 PHYLUM IX. ANNELIDA. The Segmented Worms: earthworms, leeches, etc. 

 PHYLUM X. ONYCHOPHORA. Peripatus, etc. Annelid and arthropodlike 



features. 

 PHYLUM XL ARTHROPODA. The Arthropods. Body enclosed in jointed armor. 

 Class 1. *Trilobites. (Trilobita.) Primitive arthropods. 



Class 2. Crustaceans. (Crustacea.) Lobsters, crabs, water fleas, barnacles, etc. 

 Class 3. Arachnids and Kin. (Chelicerata.) King crabs (Xiphosurida), sea 

 spiders (Pycnogonida), *eurypterids (Eurypterida), spiders, mites, scorpions 

 (Arachnida). 

 Class 4. Millipedes and Kin. (Diplopoda, Pauropoda, Symphyla.) 

 Class 5. Centipedes. (Chilopoda.) 



Class 6. Insects. (Insecta or Hexapoda.) Springtails, bristletails, grasshoppers, 

 dragonflies, bugs, beetles, flies, butterflies, bees, etc. 

 PHYLUM XII. CHORDATA. The Chordates. With notochord, hollow dorsal 

 nerve cord, and gill pouches or slits in pharynx. 



Subphylum A. Primitive Chordates. Protochordata: acorn worms, sea squirts 

 or tunicates, Amphioxus. Without cranium, jaws, backbone, or paired 

 appendages. 

 Subphylum B. Vertebrates. (Vertebrata or Craniata). With cranium and 

 backbone. 



Class 1. Jawless Fishes. (Agnatha.) Without true jaws or paired appendages. 

 Sublcass 1. *Ostracoderms. (Ostracodermata.) Bony, armored. 

 Subclass 2. Lampreys and Hagfishes. (Cyclostomata.) Bone lost. 

 Class 2. *Primitive Jawed Fishes. (Placodermi.) Bony; primitive jaws. 

 Subclass 1. *Acanthodians. (Acanthodii.) "Spiny sharks." 

 Subclass 2. *Arthrodires. (Arthrodira.) Joint-necked fishes. 

 Subclass 3. *Antia,rchs. (Antiarchi.) Flippered fishes. 



Subclass 4. *Stegoselachians. (Stegoselachii.) The remaining placoderms, 

 sometimes called "the funny fishes." 

 Class 3. Sharks and Rays. (Chondrichthyes.) Bone lost, skeleton cartilagi- 

 nous; jaws advanced in structure; scales placoid. 

 Class 4. Bony Fishes. (Osteichthyes.) Bone retained; jaws advanced in struc- 

 ture; scales various. 



Subclass 1. Choanate (Internal-nostrilled) Fishes. (Choanichthyes.) Includes 

 the lungfishes (Dipnoi), *lobe-finned fishes (Crossopterygii), and coela- 

 canths (Coelacanthi). 

 Subclass 2. Ray-finned Fishes. (Actinopterygii.) Includes the "ganoids" and 

 the modern teleosts (Teleosti), the dominant fishes of the recent fresh 

 waters and seas. 



