Palaeozoic Arachnida of North America. 13 



Sub-class II. Euarachnida 



Grade a. Delobranchia, Lankester (vel Hadropneusta Pocock) 

 Order i. Xyphosura 



2. Gigantostraca 

 Grade b. Embolobranchia, Lankester (vel Aeropneustea 

 Pocock) 

 Section a. Pectinifera 

 Order i. Scorpionidea 



Sub-order a. Apoxypoda 



b. Dionychopoda 

 Section /9. Epectinata 

 Order 2. Pedipalpi 



Sub-order a. Uropygi 

 Tribe i. Urotricha 

 2. Tartaridea 

 Sub-order b. Amblypygi 

 Order 3. Araneae 



Sub-order a. Mesothelae 



b. Opisthothelae 

 Tribe i. Mygalomorphae 

 2. Arachnomorphae 

 Order 4. Palpigradi (= Microtelyphonidae) 

 Order 5. SoJifugae (= Mycetophorae) 

 Order 6. Pseudoscorpiones (= Chelonethi) 

 Sub-Older a. Panctenodactylii 

 b. Hemictenodactylii 

 Order 8. Opiliones 



Sub-order a. Laniatores 



b. Palpatores 



c. Anepignathi 

 Order 9. Rhynchostomi (= Acari) 



Sub-order a. Notostigmata 



b. Cryptostigmata 



,, c. Metastigmata 



,, d. Piostigmata 



,, e. Astigmata 



f. Vermiformia 



g. Tetrapoda 



This classification does not include some of the extinct orders 

 and involves several assumptions which possess as yet only the value 

 of more or less useful hypotheses. In his article on Arthropoda in the 



