Geological Chronicle
Lamarck is situated in the southwestern part of the Moon, measuring 114.65 kilometers across. Subsequent impacts have heavily damaged its outer wall, leaving behind a disintegrated rim that forms a low, irregular ridge across the surface.
The northern portion of the crater is overlain by the walled plain Darwin, while Byrgius lies to the southeast. Ejecta from the Mare Orientale basin to the east blankets sections of the crater, surrounding an uneven, rolling floor whose most notable internal feature is the tiny, bowl-shaped crater Lamarck B.
The surrounding landscape contains heavily degraded satellite features, including Lamarck A attached to the southwestern rim and the huge, barely recognizable outline of Lamarck D to the west. The formation honors the French naturalist Jean-Baptiste Lamarck.