BY W. S. DUN, W. H. RANDS, AND PROFESSOR DAVID. 301 



Austrian deposits. He remarks that the Tertiary and Cretaceous 

 Diatoms show a very marked resemblance to living forms. 



Unfortunately we have not at present access to most of 

 Ehrenberg's works. 



Cayeux* has also recorded the occurrence of Cretaceous Diatoms 

 in France. In these deposits the skeleton is replaced by carbon- 

 ate of lime. 



These Diatoms are referred chiefly to Triceratium. 



Riistf has figured a G osciyiodiscns from the coprolites of the 

 Jurassic strata of Ilsede in Hanover, and from the same rocks 

 several species of the infusorian l^intinnus. 



Count Castracane| has described what he considers to be 

 Diatoms from the Carboniferous rocks of France, England and 

 Scotland. 



The origin, however, of these diatoms is questioned by many 

 pala3obotanists, the general opinion being that they are adventi- 

 tious rather than in situ. 



(b) Radio^aria. — As regards radiolaria, the remains of these 

 exclusively marine micro-organisms have been found in sedi- 

 mentary rocks of almost all ages, and Cretaceous forms have been 



* Cayeuz (L. ), Contribution a 1' t^tude des Terrains Sedimentaires. M(hn. 

 8oc. Geol. Nord.iw., 2. See specially pp. 61, 375, 458. 



He says, op. cit., p. 458, " Celles [Diatomees] que j'ai observees sont 

 independantes des silex J'en ai trouv^ dans la craie a /. [Inoceravna^] 

 labiatus de la vallee du Cher et dans la craie a M. hrevijwrus du Bray. 

 Elles sont extremement rares de part et d' autre. La determination n'en 

 est pas encore faite. J'en ai egalement s ignal6 la presence dans le 

 Campanien silicieux du S. O. du Bassin." 



Also, " Sur la presence de nombreuses Diatom6es dans les gaizes juras- 

 siques et crt^tacees du Bassin de Paris. De 1' existence de Radiolaires dans 

 les gaizes cretac^es de ce meme Bassin." Ann. Soc. Geol. Nord. xx., 1892, 

 pp. 57-60. 



t Rust, Beitrjige zur Kenntniss der fossilen Eadiolarien aus Gesteinen des 

 Jura. Palaeontographica, xxxi,, pi. xliv. (xlx.), p. 320. 



+ Comptes rendus Acad. Sci., Paris, 1874, Ixxix., p. 52. 



