AFFINITIES AND ZOOIOGICAI POSITION. 67 



exhibits, one of these being a reproduction of the excellent 

 figure given by Professor Busk {loc. cit) I have also repro- 

 duced the figure given by Mr Waters of the surface of H. 

 pellictUata, as it shows characters which merit a moment's 

 attention in this connection. The left-hand portion, namely, 

 of this figure (fig. 8, d) shows the mouths of the interstitial 

 tubes or cancelli, as well as some of those belonging to the 

 proper zooecia, to be closed by a thin calcareous pellicle, 

 which is left after incineration, and which exhibits the pecu- 

 liarity that it is perforated with numerous minute apertures 

 opposite to the mouth of each of the interstitial tubes. The 

 right-hand portion of the same figure shows the character of 

 the surface, where the pellicle just alluded to has been re- 

 moved. There can be no question that the existence of such 

 a calcareous (or more usually chitinous), surface-pellicle, clos- 

 ing the cell-mouths, is a feature which speaks strongly for 

 Polyzoan affinities ; but it should not be entirely lost sight 

 of that very similar structures occur in certain extinct types 

 which would almost universally be referred to the corals, and 

 which, at any rate, are very unlike the ordinary forms of 

 Polyzoa. Thus it is well known that various species of 

 Favosites (such as F. Forbesi, Ed. and H., var. tiiberosa, 

 Rominger, F. turbinata, Billings, and F. clatisa, Rominger) 

 are liable to have the mouths of the corallites closed by a 

 calcareous pellicle, which may cover a large part of the 

 surface of the colony. 



It only remains to add, with regard to the general external 

 characters of H. neozelanica, that the mouths of the tubes, 

 even when fully exposed by maceration in sea-water (as in 

 fig. 8, b), do not appear to show any signs of radiating spines 

 (" septa "), though, as will be subsequently seen, such really 

 exist in the interior of the cells. It may also be noted, as 

 compared with any ordinary Monticuliporoid, that though the 

 skeleton is clearly dimorphic, in the sense that it is made up 

 of two sets of tubes, the difference between the large tubes 

 (zooecia) and the small ones (cancelli) is slight and sometimes 



