572. The third layer of the palmar group of muscles of the right forearm: Flexor profundus digitorum or flexor perforans muscle, and flexor longus pollicus muscle. In the fourth layer, we see a portion of the pronator quadratus muscle. Lumbricales muscles, and the superficial of the thenar and hypothenar eminences: Abductor brevis pollicus, adductor pollicis, flexor brevis pollicus, flexor brevis minimi digiti and abductor minimi digiti muscles