A series of palatal consonants in Primitive Adûnaic, roughly equivalent to the consonants of the k-series (velars) palatalized to the y-position (SD/416). Most consonants in the series seem to have changed early: the voiceless palatals all became [s] and the voiced palatal stop ✶[ɟ] became [z] (SD/418). Later developments seem to have been the same as with those consonants. The only consonant of the c-series that survived was [j]. The main evidence for the existence of this series are archaic letters on some old inscriptions, plus some indirect evidence from the phonetic development [z] and Elvish loan words (SD/418-9).