APPENDIX 227 



Division i. Xiphosura. Large marine arachnoideans with a long, spike- 

 like telson. Ex. Limulus. 



Division 2. Arachnida. Usually air-breathing arachnoideans with six 

 pairs of appendages. 



Order i. Scorpionida. Large arachnids with a long, segmented abdomen 

 ending in a poisonous sting. Ex. Scorpio. 



Order 2. Palpigradi. Minute arachnids with a long, segmented caudal 

 tilament. Ex. Kcenenia. 



Order 3. Pedipalpi. Arachnids with a constriction between the cepha- 

 lothorax and the segmented abdomen. Ex. Thelyphonus. 



Order 4. Solifugae. Arachnids with a constriction between the head and 

 thorax. Ex. Galeodes. 



Order 5. Pseudoscorpionida. Arachnids without a constriction be- 

 tween cephalothorax and abdomen ; pedipalps chelate and very long. Ex. 

 Chelifer. 



Order 6. Phalangida. Arachnids with extremely long, slender legs and a 

 segmented abdomen. Ex. Phalangium. 



Order 7. Araneae. Spiders. Arachnids with a constriction between the 

 cephalothorax and the unsegmented abdomen. Ex. Agelena. 



Order 8. Acarina. Mites. Arachnids with body not divided into ceph- 

 alothorax and abdomen, and unsegmented. Ex. Hydrachna. 



Order 9. Linguatulida. Parasitic arachnids with ringed, vermiform body. 

 Ex. Pentastomum. 



Order 10. Tardigradi. Minute, aquatic arachnids. Ex. Macrobiotus. 



Order 11. Pycnogonida. Sea spiders. Marine arachnids with very long 

 legs. Ex. Pallene. 



Class 3. Tracheata. Air-breathing arthropods with one pair of an- 

 tennae. 



Division i. Onychophora. Wormlike tracheates with indistinctly seg- 

 mented body and appendages. Ex. Peripatus. 



Division 2. Myriapoda. Wormlike tracheates with distinctly segmented 

 body and appendages. 



Order i. Progoneata. Body mostly cylindrical and with two pairs of 

 legs to a segment. Ex. Julus. 



Order 2. Chilopoda. Centipeds. Flattened myriapods with one pair of 

 legs to a segment. Ex. Lithobius. 



Division 3. Insecta. Insects. Tracheates with body divided into head, 

 thorax, and abdomen; with three pairs of legs and usually two pairs of 

 wings. 



Order i. Aptera. Minute, wingless insects without metamorphosis. Ex. 

 Lepisma. 



Order 2. Pseudoneuroptera. Insects with two pairs of net-veined wings, 

 biting mouth parts, and incomplete metamorphosis, Ex, Dragon fly. 



