416 Dr. H. A. Nicholson on the Minute 



The surface in well-preserved specimens exhibits the apertures 

 of the ordinary corallites, interspersed with numerous smaller 

 openings, some of the latter being exceedingly minute ; but 

 in their more ordinary state of preservation the mouths of the 

 smaller tubes can only be made out with difficulty or not at 

 all. In any case, the larger corallites are rounded in form, 

 and their mouths are encircled by thickened walls. The 

 general appearance of the surface is thus very similar to that 

 of Heteropora neozelanica^ except that the small tubes are 

 disproportionately minute as compared with the larger ones. 

 We shall see also that the small tubes differ from the " inter- 

 stitial tubes " of Heteropora in having a special internal 

 structure unlike that of the ordinary corallites. With regard 

 to the internal structure of Monticulipora Jamesi : we shall 

 briefly examine the same three sets of sections as have been 

 described in the case of Heteropora. 



(a) Tangential sections, — These (fig. 4, A & B) exhibit the 

 rounded or oval apertures of the larger corallites, which 

 occupy the greater part of the section. Mixed up with these, 

 at all their angles of junction, are numerous smaller corallites, 

 which differ from the larger tubes both in size and in their very 

 irregular though mostly angular shape. Lastly, placed at 

 the angles of junction of the tubes previously mentioned, or 

 intercalated in the wall between two contiguous corallites, we 

 observe a great number of dark rounded bodies, which are 

 the cross sections of a series of strong but really hollow 

 tubes with thick walls and an exceedingly small central 

 cavity. These " spiniform corallites," as I have elsewhere 

 termed them, may be with considerable probability regarded 

 as representing a series of rudimentary or specially modified 

 corallites ; and they form a peculiar and characteristic feature 

 in many Monticuliporce ; but I cannot discuss their nature 

 in this place. The walls of the tubes, as seen in sections of 

 this nature, are thickened ; but the line of demarcation be- 

 tween the walls of contiguous corallites is always distinctly 

 recognizable, except occasionally in the boundaries between 

 some of the smaller tubes. Lastly, it is to be noted that there 

 are absolutely no traces of any canal-system in the walls of 

 the corallites, or of any pores which might place the visceral 

 chambers in communication with one another ; nor can we 

 discover the slightest indication of any thing of the nature of 

 radiating septal spines or lamella?. 



(b) Transverse sections show centrally (as already pointed 

 out in the case of Heteropora) the transversely divided tubes 

 of the axis of the branch, while marginally they exhibit the 

 tubes of the exterior thickened zone cut nearly longitudinally, 



