REPORT OX CORALS— HYDROCORALLIN^E. 55 



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 planulse 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 XL 

 fig. 9, E N). 



Spinipora, Moseley. 



Amongst the other Stylasteridse 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 allied to Errina, 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. 



Ccenosteum of Spinipora echinata. 



The ccenosteum (PL 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 1-1 0th of an inch, the 

 diameter of the stem itself being about 3-10tlis 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 ; 



