A Subarmalis is a garment worn under body armor for more comfort and to protect the wearer's body and shoulders from chafing.  It can also assist in keeping the tunic from becoming badly soiled from oil and rust stains.  The thick shoulder padding provides for more comfort against the weight of the armor and elevates the collar plates higher around the neck for a better fit and appearance.

Commander Marsallas wears his "Subarmalis" consisting of a double layer of sheepskin pelts attached to medium (3-4 oz) weight leather chest and back pieces to protect against body sweat from reaching and rusting the steel armor and also to prevent any rust and oil from the armor transfering back to stain the tunic.   These measures will not totally prevent the staining of the tunic;  but will certainly help.     

He stands holding his "Corbridge" type A  lorica segmentata.  The Legion's "Signum" standard is on the left.  The "hand" form at the top represents a "maniple" (latin for "Handful") unit of two 80 man "centuries".  Three Maniples would make up a "Cohors" of six "Centuria".   The meaning of the multiple discs or "phalerae" is not well understood.  It was thought that the number of phalerae indicated the number of the Century within the Cohort, since no more than six phalerae are normally displayed on a signum standard.  Truth is, we do not know what these discs on the "standard" indicated.   His "scutum" shield of the classic early Empire period,  is resting against a tripod of "palisades / sudes" stakes.  Consult the  Equipment  page for more details.