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.
The base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints, and the head with one of the first row of phalanges at the metatarsophalangeal joints. The first metatarsal articulates with the medial cuneiform, and to a small extent to the intermediate cuneiform.