106 



BRITISH STROMATOPOROIDS. 



formed by the inosculation of the horizontal connecting-processes given off by the 

 radial pillars. These pores doubtless represent the sections of imperfect zooidal 

 tubes. In fact, vertical sections sometimes show such tubes, crossed by delicate 

 transverse tabular, to be present ; but they are always very irregularly and feebly 

 developed. Both tangential and vertical sections show that the main canals of 

 the radial pillars and concentric lamina? give off secondary tubuli, which inosculate 

 to form a system of canaliculi traversing the substance of the skeleton-fibre. 

 These secondary tubuli are best seen in sections traversing the concentric lamina? 

 (Fig. 1, a). 



Fig. 16. 



Fig. 16. — A. Tangential section of Bermatostroma ScMiileri, n. sp., enlarged twelve times. 

 B. Vertical section of the same, similarly enlarged. Both sections intersect one of the 

 large thin-walled tuhes which are found at intervals in this species. 



One of the most singular features in Hermatostroma Schlilteri is to be found in 

 the fact that each successive stratum of the massive ccenosteum is traversed by a 

 series of short, wide, flexuous tubes, directed vertically to the concentric lamina?, 

 and apparently terminating inferiorly by closed ends, while they open above on 

 the surfaces of the lamina? by large rounded apertures. Thin sections (Fig. 16) 

 show that these tubes have thin proper walls of their own, and have occasional 

 internal tabula? ; and they might therefore be supposed to be adventitious struc- 

 tures. That they belong, however, to the Stromatoporoid in which they are 

 found seems to be sufficiently shown by their comparatively regular development, 

 by their being uniformly present in all parts of the mass and at all levels, and by 

 their opening on the surface by definite apertures, often placed on rounded 

 " mamelons." By the fact that they have no connection with one another, it is 

 rendered certain that they cannot belong to embedded colonies of either Aulopora 

 or Syringopora. It is difficult to see what these tubes can be, if they did not serve 

 for the lodgment of the reproductive zooids. 



There is in many respects a close relationship between Hermatostroma and 

 Idiostroma, the general arrangement of the skeletal tissue being very similar in the 

 two genera. The system of tubuli in the skeleton-fibre is, however, greatly more 



