Dr. H.A.Nicholson on the Genus Stromatopora. 9 



solved away" {loc. cit. p. 93). The materials now in my 

 hands, however, are quite sufficient to prove conclusively that 



Fig. 1. 





B 



ti, part of the under surface of a large example of Stromatopora ttibcrculata, 

 showing the concentrically wrinkled basement-layer and the openings 

 of the oscula, natural size, b, a portion of the upper surface, natural 

 size ; c, a vertical section of a frag-ment of the same, magnified to show 

 the internal structiu'e. 



these canals and apertures are truly parts of the fossil. They 

 are mostly to be detected upon the upper surface of the mass ; 

 but in one large specimen, which seems to have grown from a 

 broad base of attachment and then to have spread out laterally 

 in an irregularly cup-shaped form, they are plentifully deve- 

 loped on the lower sm-face. It can hardly be that they can be 

 any thing else than openings coiTesponding to the "oscula" 

 of sponges. The " pores " I have not yet made out with ab- 

 solute certainty ; but I believe that the surface-tubercles are 

 truly of this nature, some of them showing almost conclusive 

 proofs of having been perforated by minute openings at their 

 apices. 



I'here would thus appear to be every reason for concluding 

 that S. tuherculata is truly a calcareous sponge ; and the chief 

 question remaining is whether it can with propriety be re- 



