Do trap door spiders have 10 legs?
The definition of a leg from Merriam-Webster is


  "One of the rather generalized segmental appendages of an arthropod used in walking and crawling"


As Gerardo Furtado has already stated, the front pair of appendages are called palpi and are not used for walking, but for mating and manipulating objects. By this definition, palpi are not legs and therefore trap door spiders have 8 legs, not 10. More information on the rather large pali found on trap door spiders can be found in P.D. Hillyard's The Private Life of Spiders. 


Image from Biodiversityexplorer.org.