MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERID2E. 
44 l J 
which are slightly curved and bent inwards towards the coral stem, and at the same 
time directed towards its upper extremity. Since the larger dactylozooids were all found 
in the described condition in spirit specimens, it would appear that they are incapable of 
being retracted to a greater extent. The pores are certainly not deep enough to allow 
of their entire retraction within them, and the mode of attachment of the bases would 
not allow of such retraction. No doubt the zooids, when active and expanded, are 
long and attenuated, and the long spines on which they are borne are very possibly to 
be regarded as contrivances for giving them a long reach. A tendency to attachment 
by the side of the base, within the zooid pore, has been already noticed as occurring in 
the dactylozooids of Sporadopora dichotoma * It is here the normal condition, and 
much more fully completed. A closely similar method of attachment and retraction of 
the dactylozooids occurs in all the genera of Stylasteridm, which form regular cyclo- 
systems of zooids. 
The smaller dactylozooids are simple bluntly-conical bodies, of less than one-third 
the size of the larger form. They occupy the smaller dactylopores, and are retracted 
directly within these when at rest (Plate 38, D D). 
Gastrozoouls. — These are cylindrical in form, with a dome -like hypostome and six 
apparently simple conical tentacles, set on in a single whorl. The zooids are, as 
usual, retracted within sacs lining their pores. The tentacles in the retracted condition 
of the zooids are doubled together over their hypostom.es, with them tips bent inwards 
and downwards towards them. The zooid bases terminate in four large canals of the 
coenosarcal mesh work, and are firmly united to the styles of the pores. 
Gonophores. — No generative elements were discovered in the single specimen of 
this coral obtained for examination. 
(5.) GENUS STYL ASTER (GRAY). 
The genus Stylaster, which gives its name to the family Styl aster idte, was estab- 
lished by Gray, in 1831, for the reception of Stylaster roseus, the old Madrepora 
rosea of Pallas, and Oculina rosea of Lamark and others. The species the structure 
of which is here to be described was obtained off the mouth of the La Plata. It 
appears to have been hitherto undescribed. 
Corallum of Stylaster densicaulis, sp. n. (H. N. M.) 
The corallum (Plate 34, figs. 5, 5a) is flabellate in form, with a very stout main stem 
and branches, which make with one another angles of from 25° to 30°. The main 
stem and larger branches are oval in section, the longer diameter of the ellipse being 
at right angles to the plane of the flabellum. The stem and branches give off numerous 
comparatively small and short ramifying branchlets from their lateral margins. Occa- 
sionally as an exception a branchlet is given off from one of the faces of the flabellum 
at right angles to it, thus distorting its fan-like form. 
* See p. 437. 
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