6 Dr. H. A. jSicholson on the Genus Stroraatopora. 



compared to the vesicular coenencliyma of many tabulate 

 corals. On the contrary, it consists of successive calcareous 

 layers which may be regarded as comjwsed of an amalgamated 

 system of horizontal spicules, separated by interspaces, and 

 kept apart by a vertical system of delicate calcareous rods, 

 giving rise to a system of more or less quadrangular cells. 

 The liorizontal laminse are upon the whole continuous ; but 

 they sometimes subdivide and inosculate; and the vertical 

 pillars are decidedly irregular, being sometimes inclined at 

 various angles, and not being placed at imiform distances 

 apart even in all portions of a single specimen. Some of the 

 vertical rods appear to pass continuously through several 

 laminae and across the interspaces between them ; but the 

 greater number are confined entirely to the interval between 

 two successive laminae, not being continuous or corresponding 

 with those in the interspace immediately above or below. 

 There is no ground, so far as I am aware, for believing that 

 these vertical pillars or rods are perforated, or could possibly 

 be of the nature of tubes inhabited by the separate zooids of a 

 colony ; on the contrary, in all the formg which have come 

 under my notice, there is the strongest possible proof that 

 they are solid and imperforate. There is thus nothing in the 

 fundamental tissue or groundwork of Stroinatojwra, as above 

 described, which would necessarily preclude us fi-om referring 

 the genus to the Spongida ; nor can any stress be laid upon 

 Prof. M'Coy's argument that these organisms cannot be 

 sponges on account of their possessing a rigid and inflexible 

 skeleton, since similar reasoning would compel us to remove 

 from the Spongida a vast number of forms the zoological 

 position of which is beyond doubt. At the same time, if 

 Stromntojjora consisted wholly of the laminated and reticulated 

 tissue above described, and possessed none of those openings 

 which are so characteristic of the Sponges, then indeed the 

 genus might be more properly referred to the Foraminifera, 

 the near allies of the Sponges in some respects, but destitute 

 of the canal-system which is present in the latter. 



h. Such openings, however, can be show^n to exist in certain 

 forms of Stromatopora ; and there is strong reason for believing 

 that they will ultimately be found to be present in all. Thus 

 in S. striatella, D'Orb., and 8. concentrica^ Goldf., both 

 typical examples of the genus. Prof. M'Coy long since de- 

 scribed the existence of vermicular tubes opening on the sur- 

 face by small apertures, and passing more or less vertically 

 through the component layers of the mass (Pal. Foss. pp. 14 

 & 15). There is some ambiguity in the language used by 

 this eminent palaiontologist in describing these tubes and their 



