Explanation:
Ulothrix has a girdle-shaped Chloroplast that houses one or more Pyrenoids.
Ulothrix has a filamentous, long, unbranched, multicellular thallus. It is a freshwater alga that grows on sand, rock and other types of soil.
Where as, a common sight floating a top stagnant water, algae of the genus zygnema can be identified microscopically by its two star shaped chloroplasts per cell.