﻿HERMATOSTROMA SCHLUTERI. 



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side and concave on the other. If we are to judge from analogy, the convex sides 

 of such fragments ought to represent the upper surfaces of the mass, and this 

 view is supported by the fact that these sides (Plate XXVIII, fig. 12) are covered 

 with rounded eminences resembling the " mamelons " of the Stromatoporoids 

 generally. It is, however, possible that the mass was really basin-shaped, and 

 that the concave sides are really the successive upper surfaces. This view is 

 supported by the fact that the wide, scattered, and thin- walled tubes above 

 spoken of as perforating the coenosteum — whatever their true nature may be — 

 generally open by prominent apertures on the concave sides of the lamina?. 



In the possession of definite and "continuous" radial pillars Hermatostroma 

 Schluteri entirely resembles a true Actinostroma, but differs from the species of 

 this genus in the fact that the connecting processes of the pillars do not give rise 

 to an angular or " hexactinellid " network. On the contrary, the ccenosteal 

 meshes are oval or round ; and the aspect of tangential sections, so far as this 

 point is concerned, resembles that of similar sections of Stromatopora or Stromato- 

 porella. From these latter genera the present form is distinguished not only by 

 the complete development of the radial pillars as distinct structures, but also by 

 the fact that the skeleton-fibre is apparently not of the minutely " porous " type. 

 The other two general features distinctive of Her mato stroma Schluteri are the 

 apparent absence of astrorhizae, and the imperfect development of zooidal tubes as 

 recognisable structures. The zooidal tubes are, in fact, in general represented by 

 nothing more than the pores which pierce the successive " lamina? " of the 

 skeleton. 



The most remarkable features in the skeleton of Hermatostroma Schluteri are 

 connected with the tubulated condition of the skeleton-fibre. Vertical sections 

 (woodcut, fig. 30) show that each radial pillar is traversed by a wide axial canal, 

 which sends out horizontal prolongations into the successive laminae formed by the 

 connecting processes. The entire canal-system is more or less completely injected 

 with some opaque material, apparently an iron oxide, and the extensions of the 

 radial canals into the laminae can thus easily be followed, the crossing nodes of 

 the two sets of canals being generally more or less dilated. The laminar canals 

 also send off irregular secondary tubes, but it is uncertain whether or not these 

 open directly into the interlaminar spaces. On the other hand, an examination of 

 the surfaces of the concentric laminae, as exposed by fractures, renders it certain 

 that the axial canals of the radial pillars open by circular apertures both superiorly 

 and inferiorly (Plate XXVIII, fig. 13). Tangential sections (woodcut, fig. 31) 

 show that the large dark masses representing the infiltrated axial canals of the 

 radial pillars are connected with one another by more delicate dark threads 

 representing the canals of the connecting processes. Moreover the main axial 

 canals are commonly seen to give off subordinate and irregular prolongations, 



