Definition.—Cœlodendrida without an external bivalved lattice-mantle, with simple or branched hollow tubes, the terminal branches of which are free, not anastomosing.
Genus 727. Cœlodoras,[[343]] n. gen.
Definition.—Cœlodendrida without external lattice-mantle, with simple, not branched, radial tubes, which arise separately from the galea.
The genus Cœlodoras is the simplest form of the Cœlodendrida, and may be regarded as the common ancestral form of this and of the following family. It differs from all other members of these two families in the simple shape of the hollow radial tubes which arise from the galea, and are neither branched nor forked; the galea is very small, a flat triangular cap. Cœlodoras may be derived immediately from Concharium or Conchonia (p. [1723]), by development of the galea and the radial tubes.
1. Cœlodoras hexagraphis, n. sp.
Three straight, cylindrical, equidistant hollow tubes arise divergent from the three corners of each galea, and are about as long as the diameter of the valves, at the distal end armed with a spinulate knob. The odd sagittal (or caudal tube) is directed backwards, the two paired (or pectoral) tubes, forwards.
Dimensions.—Diameter of the valves 0.16, length of the tubes 0.2.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
2. Cœlodoras octographis, n. sp.
Four hollow cylindrical tubes, slightly curved, arise divergent from each galea, and are about one and a half times as long as the diameter of the valves, at the distal end knob-shaped, and armed with four crossed, recurved teeth. Two anterior (or pectoral) tubes arise from the two frontal corners of the galea basis, and diverge forwards to right and left. Two posterior tubes (a sagittal and a caudal) arise from the posterior corner of each galea, and diverge in the sagittal plane backwards.