Dimensions.—Diameter of the valves 0.2, length of the tubes 0.3.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
Genus 728. Cœlodendrum,[[344]] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 801.
Definition.—Cœlodendrida without external lattice-mantle, with branched radial tubes, the hollow branches of which are free and never connected by anastomoses.
The genus Cœlodendrum is the first described form not only of the family Cœlodendrida, but of all Phæoconchia or bivalved Phæodaria; it is also the most common form of this group, and represented by ten different species, some of which are cosmopolitan, very common, and widely distributed. In my first description of Cœlodendrum I confounded it erroneously with some forms of Cœlodasea and Cœlographis, the separated fragments of which I had found entangled between the branches of the former. The first figures of Cœlodendrum are given in my Monograph, in 1862, Taf. xiii. figs. 1-3 (not 4) and Taf. xxxii. fig. 1 (not 2 and 3). Cœlodendrum has been derived from Cœlodoras by furcation and repeated dichotomous ramification of the hollow radial tubes which arise from the galea.
Subgenus 1. Cœlodendridium, Haeckel.
Definition.—Ramification of the hollow tubes regularly dichotomous, each branch being forked again; therefore the two terminal ramules of the last branches equal.
1. Cœlodendrum ramosissimum, Haeckel.
Cœlodendrum ramosissimum, Haeckel, 1862, Monogr. d. Radiol., p. 363, Taf. xiii. figs. 1-3.
Cœlodendrum ramosissimum, R. Hertwig, 1879, Organism. d. Radiol., p. 93, Taf. x. figs. 3, 12.