REPORT ON THE RADIOLARIA. clxxxiii 



and thus increased the known period of the developmental history of the class by many 

 millions of years ( 244). 



The great significance of the Radiolaria in geology and palaeontology has been 

 brought into new light not only by these extensive discoveries, but also by the im- 

 portant relations which have been shown to exist between the Radiolarian rocks and the 

 deep-sea deposits of the present day. In this direction the wonderful discoveries of the 

 Challenger, and especially the investigations of the deep-sea deposits by Wyville 

 Thomson (L. N. 31) and John Murray (L. N. 27), have furnished us with new and 

 valuable information (compare 236239, and 245250). The Tertiary Polycystine 

 formations of Barbados and the Nicobar Islands, with which we have been acquainted 

 for the last forty years, as also the Mesozoic Radiolarian quartzes, which have only 

 recently been made known to us from the Jura, are ascertained to be fossil repre- 

 sentatives of the same deep-sea deposits which now occur in the form of Radiolarian 

 ooze ( 237), and to some extent also of Globigerina ooze and red clay ( 238, 239), on 

 the bottom of the ocean, at depths of from 2000 to 4500 fathoms. 



These investigations into fossil Radiolaria and their comparison with recent deep- 

 sea forms have a further general significance, inasmuch as the identity of many living 

 and fossil species from the Tertiary formation has been shown beyond all doubt. In 

 this direction the numerous measurements and accurate comparisons which I have made 

 during the last ten years of the abyssal forms in the Challenger collection, and of fossil 

 species from Barbados and Caltanisetta, have brought to light many important facts. 

 In this I had the able assistance of my friend, Dr. Reinhold Teuscher (compare 250, 

 and p. 1760). Further valuable contributions in this direction are found in the careful 

 observations and comparative measurements recently published by Emil Stohr (L. N. 

 35, 1880), regarding the Radiolarian fauna of the Tripoli of Grotte in the province of 

 Girgenti, Sicily. From these it appears that the number of Miocene species which are 

 still extant, is much greater than would appear from the results of Ehrenberg. 



Ehrenberg himself, towards the end of his long and laborious life, collected the 

 results of the systematic and palseontological researches, which he had begun thirty- 

 seven years previously (L. N. 16, pp. 3-12) into the Polycystina, in two large works 

 (L. N. 24, 25). The first treatise (L. N. 24, 1872) contains the Mikrogeologische 

 Studien liber das Kleinste Leben der Meeres-Tiefgriinde aller Zonen und dessen geolo- 

 gischen Einfluss, with a list of 279 Polycystina observed by him from the deep-sea, 

 as well as figures of 127 species. The second work (L. N. 25, 1875) contains the 

 Fortsetzung der Mikrogeologischen Studien, mit specieller Riicksicht auf den Poly- 

 cystinen-Mergel von Barbados ; the list of fossil Polycystina observed by him includes 

 325 species, of which 26 are still extant ; 282 of them are figured on the thirty plates 

 accompanying the memoir. By means of these numerous figures, as well as by the 

 appended systematic and chorological tables, Ehrenberg furnished a welcome supple- 



