226 PROF. II. A. NICHOLSON AND DE. J, MURIE ON THE 



The former, crust-like expansions, had an undulating mamillated 

 contour, and in part a granular superficies. The nodular and 

 nipple-shaped elevations also sparsely showed apical perforations ; 

 and here and there the broken surface demonstrated a tendency 

 to scaly layers. Thus, what with the dirty brownish- white 

 colour of the specimens, and other visual characters, there was 

 indeed great likeness to some specimens of Stromatopora. The 

 other, densely interwoven, branching Nullipores in their general 

 configuration and chalky colour more markedly differed from the 

 ordinary Stromatoporoid appearance. 



In both series of Nullipores, however, in this mere casual out- 

 ward examination, it was interesting to note how in the weathered 

 areas and undulating exposed layers the calcareous films and subja- 

 cent often reticular substance evinced a similar disposition to put 

 on the Stromatoporoid facies. Another feature more manifest in 

 some than in others of the specimens was the presence of larger 

 tortuous and other perforations of a boring parasite, besides un- 

 doubted tortuous Serpula-tvibQ^, and foreign substances intermixed 

 in the crevices. In none of these specimens did any of the fresh 

 or weathered sections offer the special feature of Stromatopora, 

 viz. distinctly perceptible interlaminar spaces and vertical radial 

 pillars ; though, as aforesaid, in weathered superficial layers 

 minutely cribriform structure occasionally prevailed. Instead, 

 throughout the mass as a rule the dense chalky consistence ap- 

 peared to the eye or through the hand-lens. StellsB or radiate 

 water-canals are entirely absent both superficially and deeply. 



As regards their intimate and minute structure, microscopical 

 sections, made in various directions and from each and all of the 

 specimens, only confirmed what is already well known concerning 

 the histology of the Corallinace^. Their distinctive vegetable 

 cells, far more minute than any of the so-called sarcode-chambers 

 of the Stromatoporse, perfectly agreed in every detail with those 

 of the CorallinesB and Nulliporse of our own coasts — to wit, such 

 forms as Gorallina officinalis, C. incrassata, Melohesia polymorpJia, 

 and M. pitstulata, &c. 



Thus, taken as a whole, the Nullipores do not possess Stroma- 

 toporoid essentials ; and what resemblances exist between them 

 are rather a combination of superficial characters than those of 

 close or true affinity. The study and comparison of these South- 

 African Nullipores, among other things, carries with it this useful 

 lesson — that these calcareous bodies are subject to extraneous in- 



