on the Organic Composition of Chalk and Chalk Marl, 311 



The thirty-nine species of siliceous-shelled Infusoria belong 

 to fourteen genera, and are as follow : — 



Actinocyclus ternariuSi A. ^quaternarius^ A. ^quinarius, A, 

 senarins, A. septenarius, A. octonarius, A. denarius; Coccone- 

 ma CretcB\ Cornutella clathrata\ Coscinodiscus Argus, C. 

 centralis, C. lineatus, C. '^mino?-, C. *Patina; Denticella i^ra- 

 gilaria, D. tridens ; Dictyocha Fibula, D. Navicida, D. poly- 

 actis, D. specidum, D. stella, D. triangtda ; Eunotia zebra ; 

 Fragilaria rhabdosoma, F. striolata?; GaWioneWa aurichalca?, 

 G. sulcata; Haliomma Medusa, H. crenatum; Lithocampe 

 lineata, L. Radicida, L. solitaria ; Navicula africana, N. iBa- 

 cillum, N. eurysoma, N. ventricosa, N. 5/cw/« ; Pyxidicula 

 prisca ; Synedra 2//w«. 



The seven species of soft-shelled Infusoria of the flints be- 

 long to three genera, and are the following: — Chaetophyta 

 Pyrites; Peridinium pyrophorumf; Xanthidium bulbosum, X. 

 furcatum, X. hirsutum, X. ramosum, X. tubiferum. 



The five species of siliceous plants belong to two genera, 

 namely, Spongia {Tethya?) aciculosa, S. cancellata, S. ^Cri- 

 brum, S. binodis; Spongilla {Tethya?) lacustrisX, 



Of these principal forms the before-mentioned rocks partake 

 in the proportions as stated below : namely. 



The Chalk of 



Puszkary contains .. 



Riigen 



Jutland 



Gravesend 



Brighton 



Meiidon 



Cattoh'ca 



The Chalk Marl of 



Caltasinetta 



Oran 



Zante 



Greece 



The Compact Chalk of 



Egypt 



Arabia 



The Nummulite Limestone of 

 The Pyramids of Geza 



Species of 



Calcareous 



Polythalamia. 



Species of InfUsoria. 



Siliceous, Soft-shelled 

 in Cfaalk, in Flints. 



Siliceous Infusoria. 



27 

 18 



8 



9 



Species of 

 Siliceous 

 Plants. 



Containing 4 species of Num- 

 mulite, the largest of which 

 is one inch in diameter. 



t Peridinium delitiense has hitherto been found only in flint pebbles 

 near Delitzsch, yet accompanied with forms that are common in the flints 

 of the chalk. 



X In the preceding lists, the species which are marked with an asterisk * 

 are those which most frequently occur, forming the masses of the rocks. 

 The Rotalia globulosa occurs in all the localities. 



