McIntosh described r as "a voiced retroflex alveolar flap" and x as "backed alveolar . . . somewhat retroflex"; "backed alveolar" seems to correspond to the term "postalveolar" in more modern phoneticians' jargon. Among phoneticians, the alveolar ridge is seen as a range, not a point, in the sagittal (front to back) dimension of the roof of the mouth. Phoneticians optionally distinguish between "prealveolar" and "postalveolar" (and likewise between "prepalatal", "midpalatal", and "postpalatal"). It must be understood that in the jargon, "pre-" and "post-" do not have their normal English meanings. "Postalveolar" means "the rear portion of the alveolar ridge", not "a region behind the alveolar ridge", while "prepalatal" means "the front portion of the palate (immediately behind the alveolar ridge)", not "a region in front of the palate". Thus, the descriptions "backed alveolar" and ""somewhat" retroflex" are consistent (perhaps even duplicative). Grimes (1955) described the allophone symbols as "retroflex reverse flap" and [z s as "retroflex", but he amended this to "apicoalveolar affricate, fricative, and flap /t͡s r ɾ/ (the latter two with retroflex quality)". The description, "reverse flap" was not defined. By way of conjecture, it may mean that the tongue tip (apex) travels up and backward during the flap articulation instead of straight up or up and forward.