210 . THE VOYAGE OF H.M.S. CHALLENGER. 



Sporadopora dichotoma. Older specimen reduced in size to one-half of its 

 dimensions to show the method of branching in the more fully grown 

 specimens. 

 Spinipora echinata. Enlarged to twice the natural size. 



Astylus subviridis. Several of the branches of the specimen are broken off. 

 Natural size. 

 Fig. 5. Stylastcr densicaulis. Portions of a ccenosteum of the natural size, a Portion of 



a tip of a branch enlarged. 

 Fig. 6. Allopora profufida. Natural size, a Portion of same enlarged. 

 Fie;. 7. Errina labiata. Natural size. The form of the stem of the ccenosteum is much 



*■& 



distorted in places by parasitic annelids, a Portion of a branch enlarged. 



PLATE II. 



Fig. 1. Section vertical to the surface of ccenosteum of Sporadopora dichotoma 

 showing the structure of the hard parts. The general mass is seen to be 

 excessively porous in appearance, being traversed in all directions by 

 canals which, in the recent condition of the coral, contain the elements 

 of the ccenosarcal meshwork. The perforations and canals are smaller 

 towards the surface of the ccenosteum, and coarser in the deeper regions. 

 The cavities in the mass occupied by the zooids and gonophores are 

 excavated within it, and have their walls freely perforated, like the 

 remainder of the ccenosteum. 



G Z. Mouth of a gastropore. 



S. Style terminating above in a delicate brush of spicules. 



T. Thin calcareous tabula. 



D Z, D Z. Pores of large and small dactylozooids. 



G. Cavity or ampulla occupied by a male gonophore, which is in this 

 genus entirely sunken beneath the surface of the ccenosteum. 

 Fig. 2. View of the surface of the ccenosteum of Sporadopora dichotoma as seen by 

 reflected lisdit. 



G Z, G Z. Mouths of gastropores. 



D Z, D Z. Mouths of dactylopores. 



G, G, G. Shallow depressions in which the ampullae open to the 

 surface. 

 Fig. 3. Portion of the ccenosteum forming a single calicular system of Stylastcr deit- 

 sicaidis laid open by a vertical incision, in order to show the arrangement 

 of the hard parts, and enlarged. 



G Z. Gastropore. 



