Stromatoporoids and Eozoon. 341$ 



framework to that of a Dictyonine sponge. Beatricea was 

 compared to an Orthoceras-\'\kQ mollusc. 



I myself at first mistook altered chitinous rings and coils 

 for siliceous spicules, the astrorhizse for oscules, and the 

 tabula3 for diaphragms and dissepiments like tliose of Cliona, 

 and regarded the general skeletal framework as an originally 

 spicular structure altered by mineralization, for I could often 

 see rings and apparent sigmas imbedded in it. I found 

 later, however, that the supposed " spicules " were altered 

 chitinous hoops and spirals. The astrorhizfe appear to be due to 

 the fusion of several outer openings of tubuli, thereby leading 

 to the converging of finer pseudopods into main trunks. 

 PI. IX. figs. 13, 14:y representing a longitudinal vertical 

 section of Polytrenia ct/Iindricion, shows, for instance, tubuli 

 with a relatively large single external opening and one, two, 

 or three smaller inner opetiings, a compound system being 

 funnel-shaped with a cribriform month directed inwards. A 

 growth and extension of this simple system would result in 

 the formation of an astrorhiza. Further, a more careful 

 examination revealed the typical Foraminiferal structure of 

 the skeleton itself. 



What chiefly led me to regard the Stromatoporoids as 

 siliceous sponges was tlie discovery, in the sections of those 

 fossils, of little " pockets " of coiled sigma-like bodies and also 

 tubular canals lined with these bodies in scalarit'orm fashion, 

 I had seen a somewhat similar arrangement of ring-like real 

 siliceous spicules in the sponge part of " Merlia normani^'' 

 which at one stage of my devious gropings after the clue 

 to this mystery I had named Noronha scalnriformis. But 

 presently I found similarly shaped rings in the soft tissues 

 of decalcified recent Foraminifera *. Here the chitin has 

 resisted the acid used for decalcifying, and the rings seemed 

 to be chitinous, but in the fossils they looked like siliceous 

 spicules. I now examined the skeletal framework, and saw 

 that it was penetrated by tubuli and channels of communi- 

 cation between chambers. 



The so-called tabulse, which were supposed by Nicholson 

 to be similar to those of Millejyora, are dia|)!)ragras formed in 

 the chambers and in the course of the canals. 



Tliese '.' tabulse " are present in the spaces filled by the soft 

 tissues, both in the Stromatopora type and in i\\Q Actinostroma 



* Evidently the function of tlie cLitinous hoops and coils is to give 

 support to the soft mouilated branching sarcode. The swellings on many 

 of them are due apparently to lateral conjpvession arising from the pull 

 of the extensile sarcode along an axis at right angles to the plane of the 

 hoops. 



