REPORT ON CORALS—HYDROCORALLIN. 5) 
When the planula is viewed from the surface the transparent areas of the ectoderm 
are seen to be enclosed by the opaque tracts which spread round them : a condition 
more clearly marked in the case of the planule of Cryptohelia. 
The endodermal mass of the planula is composed of much granular matter, in 
which are embedded numerous small transparent cells and nuclei, also oil-globules 
of various sizes, and many nematocysts in various stages of development (Pl. XI. 
fic. 9, EN). 
Spinipora, Moseley. 
Amongst the other Stylasteridze obtained off the mouth of the La Plata, in 600 
fathoms, was a single specimen of a form, to receive which I have made a new genus, 
Spinipora. It is closely alhed to Evrrina, but shows sufficient differences in the 
structure both of the hard and soft tissues to warrant its being placed, at present at 
least, in a separate genus. 
Coenosteum of Spinipora echinata. 
The ecenosteum (PI. I. fig. 3) is in the form of a single irregularly cylindrical stem, 
bearing at its summit, in the only specimen procured, a couple of similarly shaped 
branches, The base of the stem is somewhat swollen, and encrusts the object to which 
it adheres. The whole surface of the ccenosteum is thickly beset with spinous pro- 
jections, which, being all inclined towards the tips of the branches, stand out beyond 
the main surface of the stem to a distance of as much as 1-10th of an inch, the 
diameter of the stem itself being about 3-10ths of an inch. The spines are spout- 
like in form, more or less conical, with the ends usually truncated, and their upper 
surfaces—that is, those turned towards the tips of the branches—channelled out into 
deep and wide grooves. The grooves usually commence on the surface of the spines 
as slits, and widen out to terminate at the truncate ends of the spines in wide spout- 
like mouths. The groove-like excavations are continued as tubular cavities for a short 
distance into the axes of the spines, beyond the slit-like commencement of the grooves. 
The grooves are the cavities which are occupied by dactylozooids—are, in fact, the 
dactylopores, which are here excavated within long projecting spines, and are widely 
open on one side for nearly their entire length. The small continuation of the groove 
within the axis of each spine represents the normal dactylopore. 
Two kinds of dactylopores occur in the present form: the larger ones already 
described, and much smaller pores, which are mostly placed on the bases of the 
spinous processes but occur also more sparingly on the general surface of the stem ; 
