202 DESCRIPTION OF [Polygastrica. 



fossil. It is remarkable that of the whole of the fossil 

 Infusoria, this genus is the only one which does not pre- 

 sent living representatives. On reflection, we at once 

 perceive that the central furrow of the sphere of Gal- 

 lionella, which is pierced with holes, leads to an interior, 

 having a rayed structure, which here shews distinct walls 

 of separation for each hole or opening. The structure 

 of the single, flat, dish-like body, is minutely cellular, 

 and differs in this respect from Gallionella, though an 

 approach may be seen in G. sulcata. 



219. ACTINOCYCLUS senarius. The six-celled Actino- 

 cyclus has a cellular lorica, which is discoid in shape, and 

 has six internal partitions. " The schistus of Oran," says 

 Ehrenberg, " contains great quantities of little flat dishes 

 of siliceous matter, which are very thin and (cellular) 

 in structure ; some are of greater size, and have larger 

 cells than the others ; it is doubtful whether these are or 

 are not single bodies, each perfect in itself. If they are, 

 the germs Arcella is their proper station. If two are seen 

 connected together, so as to form a flat disc-like hollow 

 box, the genus Gallionella is their situation, as G. sulcata 

 presents the same structure. Along with these disc-like 

 little plates others are seen, which are smaller in size, and 

 whose mesh-like texture forms less regular spires, but in 

 which, when under water, six walls or partitions, radiating 

 from the centre, are seen, dividing the interior into six 

 distinct chambers. The bodies evincing such formations 

 are Actinocycli." Group 132 represents different views of 

 them. Diameter 1-1 150th to l-720th. 



220. ACTINOCYCLUS octonarius. The eight- celled Acti- 

 nocyclus has a cellulose lorrca, discoid in shape, and pro- 



