Abstract: A dish structure includes: (a) a bottom container having an outer cylindrical wall and a diametric base interconnecting the outer cylindrical wall; (b) a lid having an inverted cylinder provided with a downwardly extending cylindrical wall, the lid being sized so that the downwardly extending cylindrical wall associates with the outer cylindrical wall of the bottom container; (c) a frictionally-engagable member integral with the surface of the downwardly extending cylindrical wall of the lid; (d) a frictionally engagable member integral with the surface of the wall of the bottom container; and (e) at least one of the bottom container and the lid being formed of flexibly deformable synthetic plastic material, which is thin enough to have the characteristics of being flexibly deformable. By such structure the lid and bottom container base may remain loosely assembled (unlocked), or by user manipulation be tightly assembled into a reversibly locked configuration.

Abstract: A Petri dish in which the flat bottom is provided with a plurality of preferably radial ribs is disclosed. The ribs do not project more than about 0.050 inches above the upper surface of the bottom, and preferably not more than about 0.030 inches. The thickness of the bottom portion other than at the ribs is not greater than about 0.030 inches, and preferably not greater than about 0.025 inches. Various rib arrangements are contemplated. In the preferred embodiment, there are at least three radial ribs, and preferably four ribs spaced at 90 degrees to each other. A lid having the same basic structure may also be produced. Generally any suitable rib layout could be selected. A large number of ribs could be provided, if desired, though not a requirement. The ribs need not necessarily be radial. The ribs need not necessarily be continuous, and they need not necessarily run all the way from the center to the side wall, or from side wall to side wall. The ribs need not necessarily be straight, but could be curved.