21S 



BRITISH STROMATOPOROIDS. 



which may form a loose network in the substance of the fibre, and which seem in 

 some cases to actually reach the surface of the fibre itself, so as to open into the 

 interlaminar spaces. 



Pig. 30. 



Fig. 31. 



- Q>, 



Wl 



-/ 



Fig. 30. — Part of a vertical section of Hermatostroma 

 Schliiteri, Nich., enlarged about 24 times. 



Fig. 31. — Part of a tangential section of the same, 

 similarly enlarged. 



It follows from what has been above said that, though the skeleton-fibre of 

 Hermatostroma Schliiteri is not "porous," in the sense in which this term is 

 used in connection with the ccenosteal fibre of Stromatopora, it is nevertheless 

 traversed by tubes which, in point of fact, are chiefly remarkable for their 

 exceptional size and regular distribution. It has further to be borne in mind 

 that the only known example of this species has undergone considerable change 

 in f'ossilisation, and that the apparent absence of minute pores in the skeleton- 

 fibre may be simply the result of mineralisation. This view is rendered the more 

 probable since the Hermatostroma episcopate of the British Devonians — to be 

 described immediately — has, if rightly placed in this genus, a skeleton-fibre 

 which is both porous and tubulated. 



The generic diagnosis of Hermatostroma given in the earlier portion of this 

 work (p. 105) must be, therefore, so far amended as to admit that the skeleton- 

 fibre is, in some cases at any rate, porous as well as canaliculated. A further 

 amendment has been necessitated by the examination of H. episcopate, since this 

 species possesses well-marked astrorhizas. 



I had formerly placed the genus Hermatostroma in the immediate neighbour- 

 hood of Idiosfroma chiefly on account of its possession of a skeleton which is 

 essentially reticulate, but which at the same time possesses exceedingly well- 

 developed radial pillars. Upon the whole, however, I am now rather disposed to 

 consider Hermatostroma as really one of the same series of generic types as 

 Stromatopora, Stromatoporella, and Parallelopora. The essential distinctions 



