Helictites are, perhaps, the most delicate of cave formations. They are usually made of needle-form calcite and aragonite. Forms of helictites have been described in several types: ribbon helictites, saws, rods, butterflies, hands, curly-fries, and clumps of worms.. They typically have radial symmetry.
The temporomandibular joint (TMJ) is the joint where the mandible articulates with the cranium (Fig 8.1). The following characteristics make the TMJ a complex and unique joint: 1  It is classified as a compound joint even though it does not include three bone structures in the articulation.
It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. The bone is formed from a fusion of left and right processes, and the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline.