246 On Fistulipora incrustans, Pliill. (F. minor, Jf Coy). 



bands within the branches. I am inclined to think, from the 

 evidence presented, that these thickened layers indicate 

 periods in the life of the organism in which the mesopores, 

 from some canse or other, ceased to be developed, or, 

 when present, were small and widely scattered. The evi- 

 dence also indicates that when the mesopores ceased to grow 

 the sclerenchy ma- deposit was leady to take its place, the 

 latter being seen to form a continuous uninterrupted deposit 

 upon the tubes of the autopores outwards to their surface, 

 whereas in the spaces occupied by the mesopores it only 

 alternates with the latter, but does not form a regular con- 

 tinuous outward growth. 



From the foregoing remarks it will be seen that (he British 

 Carboniferous Fistulipora presents several interesting struc- 

 tures upon which little has been formerly written, and which 

 only well-preserved specimens have now revealed. I shall 

 not at present dwell further upon these structures, nor attempt 

 to discuss any of the points relating to the zoological relation- 

 ships of the genus, beyond briefly stating that none of the 

 structures here noticed are peculiar to Fistulipora^ they being 

 found in other organisms, some of which are at present placed 

 with the Monticuliporidffi, Others with the Polyzoa. The 

 vesicular interstitial cells (mesopores) found in Fistulipora^ 

 accompanied by a perforated sclerenchyma-structure and a 

 trilobed form of the cell-mouths in the autopores, are cha- 

 racters that are present in both Scottish and American forms 

 of the Cystodictyonidee, Ulrich. Spiniform tubercles (acan- 

 tho]3ores) along with a minutely perforated sclerenchyma- 

 structure, as in F. incrustans, are also present and often 

 beautifully preserved in the Carboniferous Fenestellida^ and 

 other Polyzoans — these structures in transparent sections 

 being often quite comparable in all their characters with 

 similar structures found in the Monticuliporida3. The occur- 

 rence also of numerous radial spines in the tubes of the Car- 

 boniferous Fistulipora is another character that closely relates 

 it to Heteropora, a genus that is also found to have its cell- 

 mouths closed in certain stages, according to Prof. Nicholson, 

 ' Monticulipora,' p. 67, with " a calcareous (or more usually 

 chitinous) surface-pellicle," which he further says ''is a feature 

 which speaks strongly for Polyzoan affinities," although he 

 afterwards states that this closed condition of the cells " by 

 a calcareous pellicle " is not unknown amongst certain corals 

 belonging to the genus Favosites, the species of which he 

 names. I will, on the other hand, only state in conclusion 

 that I have also found in several species of undoubted Car- 

 boniferous Polyzoa the cells closed by a calcareous secondary 



