Eileen Fisher Viscose Jersey Knee Length Tank Dress in black, size M. Brand new with original tags, retail price $178. 92% Viscose, 8% Lycra. Machine wash  cold. Sleeveless, round neckline, empire seaming and notched hem that's slightly longer in the back. 

Measurements are approximate, taken flat and unstretched:

Underarm to underarm: 18½" across

Hem: 39" front and 41" back