104 THE VOYAGE OF H.M.S. CHALLENGER. 
lobulate, and rising in a tuft. Ccenenchym very abundant, and presenting at its surface 
a great number of rounded pores disposed with regularity and separated by projecting 
papilliform grains. These grains are formed by the upper extremities of an equal number 
of cylindrical and vertical beams, which shut in tubuliform spaces, open above, and 
divided from space to space by cross partitions. Calicles circular. Septa very little 
developed, but distinct, and twelve in number. Horizontal floors present and well 
developed. The genus is remarkable for its alveolar appearance and the tubular 
structure of the parenchym.” 
The coral is figured by Milne-Edwards, l.c. (pl. i. fig. 3, a-c). A drawing of the 
growing tip of a frond, much enlarged, will be found on Plate I. figs. 10 and 11 of this 
paper. The following points require to be remarked concerning the structure of the 
corallum. The papilliform eminences described by Milne-Edwards as covering the sur- 
face of the corallum spring from the points of apposition of the walls of several of the 
ccenenchymal tubes, very usually from the point of meeting of the mouths of four tubes 
(Pl. II. fig. 11). At these points the hard tissue consists of thickened vertical beams of 
caleareous matter, from which thin lamellar-like processes are given off. These processes 
form the walls between two contiguous tubes by crossing to join similar processes from 
adjacent beams. Each beam thus gives off four lamellar processes, which are disposed 
roughly at right angles to one another. The narrow summits of the thin lamin forming 
the sides of the tubes fall short in their centres, by a considerable distance, of the level 
of the thickened masses from which they spring, and are excavated or hollowed out at 
these spots. It is across these excavations in the lamine that the canals of the deep 
system pass in the fresh condition of the coral, by means of which the cavities of the 
tubes and polyps communicate freely with one another. The structure of the ccenen- 
chym of the coral might perhaps be better described by saying that it consists of a series 
of tubes of circular section, and of nearly uniform diameter, closely packed side by side 
more or less in regular rows, with their walls where touching fused together, and the 
spaces necessarily resulting from such an arrangement at the meeting-points of every 
three or four contiguous tubes filled in with calcareous matter, so as to form rods or beams 
of hard tissue, which are elevated above the margins of the tubes into papilliform promi- 
nences. Milne-Edwards distinguishes between the tabulee of the coenenchymal tubes and 
those of the calicles, calling the first “ traverses,” and the second “ planchers horizontaux,” 
but they are essentially similar structures. Though twelve is a common number for the 
projecting plications of the margin of the mouth of the calicle, the number is very 
variable—11, 13, 14, even 15 or 16 of these so-called septa are to be counted not 
uncommonly. In the enlarged figure of a calicle (Pl. IL. fig. 11) Dr Wild has drawn 
fifteen. The plications become less numerous at a slight depth in the calicle, and 
often here are only eight in number, with a mesentery of the polyp passing to each 
internal projection. 
