216 BRITISH STROMATOPOROIDS. 



a characteristic trellis-like appearance, the interlaminar spaces being broken up 

 into rectangular meshes. The radial pillars are traversed by very large axial 

 canals, and prolongations of these canals extend into the horizontal connecting 

 processes. Six or fewer pillars, and a like number of concentric laminae, occupy 

 a space of 2 mm., measured respectively in the transverse or vertical direction. 



Tangential sections (Plate III, fig. 1) show the broad round or oval ends of 

 the transversely divided radial pillars, with the dark infilling of the cut axial 

 canals of the pillars. Where the section corresponds with the plane of a 

 concentric lamina, the cut ends of the pillars are seen to be united into a loose 

 network, with rounded or oval meshes representing sections of zooidal tubes. 



Tangential sections also commonly show large oval or rounded apertures 

 (woodcut, fig. 16 a), which are bounded by thin but definite walls, and are placed 

 at distances of from 3 to 12 or 15 mm. apart. The apertures in question are 

 cross-sections of short, wide, flexuous tubes, which pierce the skeletal network at 

 right angles to the surface, are bounded by thin proper walls, and are crossed by 

 occasional horizontal "tabular " (woodcut, fig. 16b). Tubes of this kind seem to 

 be very generally developed in variable numbers, and they open sometimes on the 

 convex, but more usually on the concave surfaces of the lamina? (woodcut, fig. 29). 

 The nature of these tubes is quite problematical, and it is not clear that they are 



Fig. 29. 



Fig. 29. — Under (?) surface of part of a lamina of Hermatostroma Schliiteri, 

 Nich., enlarged, showing the apertures of two of the large thin-walled tubes which 

 traverse the ccenosteuin of this species at irregular intervals. 



not adventitious structures. If they really belong to the Stromatoporoid in which 

 they are found, they may perhaps be connected with the function of reproduction. 

 Obs. — All the examples of this species which I possess are fragments of a 

 single very large specimen, the complete form of which was, unfortunately, not 

 accurately noted before it was broken up. All the fragments are made up of 

 gently curved concentric layers, and are, therefore, more or less convex on one 



