The rib cage has the shape of a wide mouthed bell. That is, the superior portion of the rib cage is constricted, followed by a convex region, and the inferior portion of the rib cage expands again to have a large diameter. The phenotype is Human Phenotype Ontology identifier HP_0001591 (Bell-shaped thorax). Also known as: Bell-shaped chest, Constricted, bell-shaped thorax, Narrow, bell-shaped thorax.