ray number true uberon ray_number x ray_number N if and only if (i) x is a ray, and (ii) x is ancestrally associated with ray number N in a series of phalanges repeated along a radio-ulnar or equivalent axis, with ray_number 1 being the anteriormost ray. UBPROP:0000104 ray_number The correct terminology is yet to be established; in tetrapods 'ray' might mean the mereological sum of the phalanges of a manual digit plus a metatarsal bone (or equivalent for hindlimb)