Haloquadratum ("salt square") is a genus of the Halobacteriaceae. The first species to be identified in this group, Haloquadratum walsbyi, is highly unusual since its cells are shaped like flat, square boxes.
Merismopedia (from the Greek merismos [division] and the Greek pedion [plain]) is a genus of cyanobacteria found in fresh and salt water. It is ovoid or spherical in shape and arranged in rows and flats, forming rectangular colonies held together by a mucilaginous matrix. Species in this genus divide in only two directions, creating a characteristic grid-like pattern.
Near the end of his life, Frank Lloyd Wright stated that “there is no square in nature–nature knows only circular forms.”
[As quoted in Robert C. Twombly, Frank Lloyd Wright: His Life and His Architecture (New York: John Wily and Sons, 1979), 321]