98 
THE VOYAGE OF H.M.S. CHALLENGER. 
that of the Membraniporiche, against which location, however, there seem to me to be 
very cogent reasons. In the first place, among the forty or fifty recent and other forms 
belonging to that Family, there is none, so far as I am aware, in which the cells are 
disposed in transverse series, nor any in which the surface is divided into angular areas 
by continuous ridges which apparently belong, as in all the Salicornariadse, not to the 
individual zooecia, but seem to form a continuous network within which the latter are con- 
tained. In the Salicornariadse this continuous network is indicated, as before stated, by 
slender chitinous continuous hollow threads, and such may be contained within the thick 
calcified ridges in the present species, or may have been detached with the common 
epitheca by which they were originally clothed, but which in the single old and worn 
specimen afforded by the Challenger collection have become lost. Nor among the 
Membraniporidse am I aware that any have a central aperture with a beaded and thickened 
border. 
On the other hand, the chief, if not the only obvious, character in which any 
important divergence from the rest of the Salicornariadse is exhibited, is the existence of an 
aperture larger than the true orifice. 
All that is wanting to put the question of the Salicornarian affinities of the present 
species at rest, would, be the existence of a chitinous ring or of lateral trabeculse around or 
on the sides of the orifice. But whether such a provision existed in the superficial epitheca, 
or may be still contained in the thickened border of the aperture, I have not been able to 
make out. A remarkable peculiarity of Melicerita dubia is the extremely dense, hard, 
semi-transparent texture of the zoarium. 
Family XV. Tubucellariada. 
Cdlaridce (pars), d’Orb. 
Salicornarndce (pars), Macgilliv. 
Porinidce (pars), Hincks. 
Character . — Zoarium erect ; radicate, composed of cylindrical internocles. Zooecia 
disposed round an imaginary axis, convex, distinct, pyriform ; peristome produced, 
tubular. Surface reticulato-punctate or simply punctate with or without a simple 
median pore on the front (often wanting). Avicularia and ooecia 0. 
The Family here contains the following genera : — 
1. Tubucellaria, d’Orbigny. 
(1) Tubucellaria opuntioides, Pallas (PI. XXIV. fig. 7, and PI. XXXVI. fig. 19). 
(2) Tubucellaria hirsuta , Lamx. (PI. XXXVI. fig. 18). 
2. Siphonicytara, n. gen. 
Siphonicytara serrulata , n. sp. (PI. XV. fig. 2). 
