186 INVERTEBRATE ZOOLOGY 



Subclass I. Arachnoidea. Arthropods lacking antennae and with 

 body usually consisting of cephalothorax and abdomen. 



Division I. LIMULOIDEA. Large marine arachnoideans with a 

 long spike-like telson. Ex. Limulus. 



Division II. ARACHNIDA. Usually air-breathing arachnoideans 

 with six pairs of appendages. 



Order 1. SCORPION IDE A. Large arachnids with a long seg- 

 mented abdomen ending with a poisonous sting. Ex. Scorpio. 



Order 2. SOLPUGIDEA. Arachnids with distinct head and 

 thorax. Ex. Galeodes. 



Order 3. PSEUDOSCORPIONIDEA. Arachnids with cephalo- 

 thorax not constricted from abdomen ; pedipalps very long and 

 chelate. Ex. Chelifer. 



Order 4. PEDIPALPI. Arachnids with cephalothorax dis- 

 tinctly constricted from abdomen. Ex. Thelyphonus. 



Order 5. PHALANGIDA. Arachnids with extremely long, 

 slender legs ; harvest men. Ex. Phalangiurn. 



Order 6. ARANEIDA. Arachnids with unsegmented abdomen 

 and cephalothorax ; spiders. Ex. Epeira. 



Order 7. A CA RINA. Arachnids with body not divided into cepha- 

 lothorax and abdomen, and unsegmented ; mites. Ex. Hydrachna. 



Order 8. TARDIGRADA. Minute aquatic arachnids. Ex. 

 Macrobiotus. 



Order 9. PYCNOGONIDA. Small marine arachnids ; sea spi- 

 ders. Ex. Pallene. 



Order 10. PENTASTOMIDA. Parasitic arachnids with ringed, 

 vermiform body. Ex. Pentastomum. 



Subclass III. Tracheata. Air-breathing arthropods with one pair 

 of antennas. 



Division I. PROTRACHEATA. Worm-like tracheates with indis- 

 tinctly segmented body and appendages. Ex. Peripatus. 



Division II. MYRIAPODA. Worm-like tracheates with distinctly 

 segmented body and appendages. 



Order 1. CHILOPODA. Depressed myriopods with one pair of 

 legs to a body-segment ; centipeds. Ex. Lithobius. 



Order 2. DIPLOPODA. Cylindrical myriopods with two pairs 

 of legs to most body-segments ; millipeds. Ex. Julus. 



