Same entry in ps.-Zonaras; similar one, according to Adler, in the Ambrosian Lexicon. They exhibit confusion between the prefix stem a)rxi- ('chief', 'foremost') and the related but distinct adjective a)rxai=os ('ancient').
LSJ s.v. accepts a)rxi/klopos as a nominative, as glossed here. It might, however, be the genitive of a)rxi/klwy (Plutarch, Aratus 6.2: genitive plural), here morphologically defective -- a)rxi/klopos rather than a)rxi/klwpos -- and misconstrued as a nominative.