The Holothurian Fauna of Cook Strait, New Zealand
Diagnosis: Tentacles with one to two pairs of digits, but no terminal digit. Spicules large tables or plates, or small crossed cups or irregular bodies. No phosphatic bodies, but discolouration of the skin may occur in older individuals of some species (Deichmann, 1960).
The genera within this family, in contrast to those in the family Molpadiidae, are clearly defined, the calcareous deposits of the skin being particularly useful as criteria for separation. The deposits are not transformed into phosphatic material as are those of so many species in the family Molpadiidae, although in some cases the deposits are known to change shape with growth and age, but this change is by no means a dramatic one.
Four genera are recognised at the present time. Acaudina Clark is readily distinguishable from the rest as its tentacles have one pair of digits, while the other genera have two pairs of digits per tentacle. Paracaudina Heding has characteristic deposits in the form of "crossed cups" (Plate IV, fig. 2). Caudina Stimpson has deposits which usually take the form of spired tables and knobbed buttons. Hedingia Deichmann has distinctive tables and plates of considerable size.page 17
Plate III.—Neocucumella bicolumnata (Dendy and Hindle).—Fig. 1, tables; fig. 2, tentacle deposits; fig. 3, abnormal tables.
Molpadia violacea (Studer).—Fig. 4, rod from anterior end of body; fig. 5, developmental stage of perforated plate; fig. 6, rods from the tail; fig. 7, deposits from the middle of the body; fig. 8, rods from the posterior of the body, near the tail.
The family is cosmopolitan, with representatives in all seas. Most species are known from moderate depths, although Hedingia albicans has been taken from depths in excess of 1500 fathoms.
Genus Paracaudina Heding is represented in the Cook Strait region by a single species.