■() 



BRITISH STROMATOPOROIDS. 



them, the tubes are intersected by distinct tabulse (Fig. 9, b), and the skeleton itself 

 shows a more or less conspicuous composition out of thin concentric laminas, only 

 the thin surface-layer being at any given moment actually alive. Lastly, Mr. 

 Quelch has recently described the reproductive organs of a new species of Mille- 



Fig. 9. 



m 



o 



v~ 







B 



Fig. 9. — Thin sections of Millepora, sp., enlarged about thirty-five times. A. Tangential section. 

 B. Vertical section, g g. Gastropores ; d d. Dactylopores ; c c. Crenosarcal canals. 



pora (M. Murrayi), as having the form of circular cavities or " ampullse," contained 

 within the reticulated spongy skeleton, and covered superficially by a thin porous 

 layer which is often broken away (' Nature,' October 2nd, 1884). In the other 

 species of Millepora the reproductive organs have not hitherto been detected; but the 

 above discovery is sufficient to confirm the relationship between the Milleporidce 

 and the Stylasteridce, which had been previously established by the researches of 

 Professor Moseley. 



It will be seen from the above brief description of the structure of the skeleton 

 in Millepora, that there is a considerable resemblance between it and the skeleton 

 of certain of the Stromatoporoids. This is most conspicuously exhibited when we 

 compare with Millepora the forms which constitute the genus Stromatopora, 

 Goldfuss. Thus, in the typical Stromatoporce, such as S. concentrica, Goldf. (Plate 

 XI, figs. 16 and 18), or S. typica, Rosen. (Plate V, figs. 14 and 15), or 8. Hiipschii, 

 Barg., sp. (Fig. 6), the skeleton is composed of a trabecular calcareous network, 

 traversed by vertical zooidal tubes, which are placed in communication by means 

 of numerous ramifying coenosarcal canals. Moreover, the zooidal tubes are provided 

 with transverse "tabulae" as they are in Millepora. The principal distinctions, in 

 fact, between the skeleton of such types and that of Millepora are that the zooidal 

 tubes of the former are not, as a rule at any rate, divided into two distinct series 



