"The nun is invested with a crown, ring, stole and maniple, the last being worn on the right arm. These ornaments the nun only wears again on the day of her monastic jubilee, and after her death on her bier. It is a consecrated nun who sings the Epistle at the conventual Mass, though without wearing the maniple. At Matins, if no priest be present, a nun assumes the stole and reads the Gospel."
From the Catholic Encyclopedia.