Gate obliquely ovate. Ring obliquely ovate, with three complete prominent edges and with numerous (ten to twenty or more) simple, short conical spines, arising in three series from the three edges; commonly some smaller spines at the base.
Dimensions.—Diameter of the gate 0.1 to 0.2; length of the spines 0.005 to 0.02.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
Genus 404. Dendrocircus,[[23]] Haeckel, 1881, Prodromus, p. 447.
Definition.—Stephanida with a simple dipleuric or bilateral ring, armed with branched spines, without typical basal feet.
The genus Dendrocircus has the same dipleuric or bilaterally symmetrical form of the sagittal ring as its ancestral genus Zygocircus. It differs from the latter in the development of branched radial spines, and therefore bears to it the same relation as the amphithect Lithocircus does to the simpler Archicircus.
1. Dendrocircus quadrangulus, n. sp.
Gate irregularly quadrangular or nearly semicircular. Ring quadrangular, edgeless, with four unequal sides; ventral rod more curved and with longer sides than the dorsal rod. From the four edges arise four strong, irregularly branched spines, about as long as the diameter of the gate, with curved branches; the ventral and basal spines larger than the dorsal and apical spines. Similar to Lithocircus quadricornis (Pl. [81], fig. 9), but less branched, and with a striking difference between the shorter dorsal and the longer ventral rod.
Dimensions.—Diameter of the gate 0.04 to 0.06; length of the spines 0.05 to 0.07.
Habitat.—North Pacific, Station 256, depth 2950 fathoms.