140 SKETCH OF THE IXFUSORIA 



Ly.-irs ElomcHts of Geology, p. 39, (Am. edit.) and in Pritch- 

 ard's Hist. Inf. lig. 129-130. I have often seen in bogs and 

 small streams, huge quantities of a ferruginous colored flocculent 

 matter, whieli dispersed with gi-eat ease when toviched, and in 

 which 1 have so/nelimes been able to see, by means of the mi- 

 croscope, excessively minute filaments, which were apparently 

 moniliform. 1 believe these filaments to be the G.ferriig-inea of 

 Ehrenberg, \\-hicli is the same as the OsciUatoria ochracea of 

 various algologists. The filaments are fragile and incombustible, 

 and are said to be composed of sihcate of iron. (See Pritchard's 

 Hist. Inf. p. 199 and 200.) 



ACTINOCYCLUS. 



Free, carapace simple, bivalve, {siliceous) foi'm cylindrical, 

 [discoid) divided internalhj by several radiating partitions ; spon- 

 taneous division i)nperfect, in form of a chain. 



Ehrenberg mentions seven species, namely, A. ternarius, A. qua- 

 ternarius, A. quinarius, A. senarius, A. septenarius, A. octonarius, 

 and A. denarius, distinguished respectively by the number of 

 cells formed by the radiating partitions. Several species occur 

 in the " schiste of Oran " in Africa, in a fojmation which M. Rozet 

 considered as tertiary, but which Ehrenberg suspects is more 

 nearly connected with the chalk. 



It appears to me to be an interesting fact, that the remarkable 

 marine infusorial deposit discovered by Prof W. B. Rogers in 

 the tertiary formation of Virginia, appears to agi-ee with the in- 

 fusorial conglomerate of Oran, in containing . several species of 

 Actinocyclus, together with Gaillonella sulcata, and beautiful 

 punctate discs, which I suspect belong to the genus Coscinodis- 

 cus. I have seen no account of this last genus, but its name 

 appears peculiarly appropriate to the sieve-like discs which form 

 so large a portion of the infusorial stratum of Richmond, Va. 

 Ehrenberg mentions Coscinodiscus patina as predominating in 

 the deposits of Oran, Zante, Caltasinetta, &c. (See Weaver's 

 View of Ehrenbcrg's Observations in Lond. and Ed. Phil. Journ. 

 for May, 1841, p. 393.) In PI. II, figs. 9, 10, and 11, are repre- 

 sented several fossil species of Actinocyclus from Richmond ; the 



