450 MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERIDiE. 
The pores are arranged in regular symmetrical cyclo-systems, a circular group of 
dactylopores surrounding in each system a single centrally-placed gastropore. The 
pores of both kinds occur only arranged in these systems in this species.''’" The cyclo- 
systems so closely simulate in appearance the calicles of ordinary Hexactinian corals, 
that the genus Stylaster and its allies, such as Allopora and Crypiohelia, have hitherto 
been placed amongst the Oculinidse. The cyclo-systems in the present species appear as 
small cylindrical masses of calcareous matter, which have a somewhat greater diameter 
at the free extremity than at the base. In the growth of the coral new systems bud 
off from the sides of the older cylinders, at the tips of the branchlets. The cylinders 
thus newly formed have their axes at right angles to those of the old systems to which 
these are attached, but in the same plane with them, which is also that of the entire 
flabellum. The branchlets of the corallum, already described as given off by the main 
stem and branches, are composed of zooid systems thus related to one another. In 
the more recently formed twigs the arrangement described is plainly apparent, and 
they have thus a zigzag appearance ; but in proportion as the branchlets are traced 
nearer and nearer to the stems from which they spring, this zigzag arrangement 
becomes more and more obliterated by deposit of ccenenchym, and in the older regions 
of the corallum, on the sides of the main branches and stem, the mouths only of the 
zooid systems remain unburied by the swollen dimensions of the support. 
No pore systems occur on either of the flabellar faces of the stem or branches. Short 
branchlets, as well as single pore systems, are evidently swallowed up, to some extent, 
by the spread of ccenenchym and increase of the dimensions of the stem, and all stages 
of the process appear at the lateral margins of the stem near its base. But in order to 
secure an excessive strengthening of the stem, with the least amount of encroachment 
upon early-formecl pore systems, the stem swells to the greater extent in the direction 
of its surfaces which correspond with the faces of the flabellum and bear no pore 
systems. Hence, as already described, it becomes oval in section, being flattened in a 
plane at right angles to that in which the younger branchlets are compressed. 
The cyclo-systems are groups of zooid pores as already described, which have a 
regular symmetrical arrangement, a single gastropore in each system being surrounded 
by a circlet of dactylopores. The centrally placed gastropore in each system is a wide 
tubular cavity, with a circular transverse section. This pore is much deeper than its 
surrounding dactylopores, and has at its bottom a short stout style, with a brush-like 
conical tip (Plate 35, fig. 3, S). Just above the level of the top of the style is a 
circlet of small rough projections, which stand out from the wall of the gastropore, and 
contract its bore at this point. 
* In another species of Stylaster, S. granulata, dredged off Ascension Island in 420 fathoms, small 
isolated dactylopores were observed to occur on the surface of the corallum, as a rare exception, apart 
from the pore systems. One such was observed situate on the side of a cylindrical cyclo-system, and two 
others at the margin of an ampullar prominence. These were very probably occupied, in the recent state 
of the coral, by small dactylozooids, the rudiments of those which, in an earlier stage of evolution of the 
Stylasterid®, overspread the srarface of the ancestral form, as in Sporadopora. 
