or MAZARUNI, a river in British Guiana, rises in Lat. 4° 30' N., Long. 60° W.; and flows in a very irregular and circuitous course, generally N.E., till it joins the Cuyuni, and falls into the estuary of the Essequibo. This river has been explored for about 400 miles from its mouth; its course is interrupted by numerous rapids, which are generally divided by blocks of granite into many separate streams. In the lower part of its course it contains numerous small islands. The scenery of its upper course is mountainous, consisting of bold perpendicular granite cliffs.