880 RiEDEL [chap. 33 



niicropaleontologists, but within the last 20-30 years the planktonic forms have 

 come in for more intensive study. From the vohnninous hterature produced by 

 many authors, it is possible to refer here to only a few papers which indicate 

 the history of the use of planktonic Foraminifera for regional and inter-regional 

 correlation. As an indication of the degree of precision attainable by paleonto- 

 logical correlation, it might be pointed out that within the Tertiary, for example, 

 an inter-regional correlation confidently established within limits of ± 5 million 

 years would be regarded as satisfactory by present-day standards. Grimsdale 

 (1951) showed that the succession of planktonic foraminiferal species in the 

 Tertiary of the Middle East is remarkably similar to that in the region of the 

 Caribbean and Gulf of Mexico. Bronnimann (1950), Beckmann (1953), Bolli (in 

 Loeblich et al., 1957) and Blow (1959) investigated Tertiary planktonic assem- 

 blages in the Caribbean region and their relationship to faunas of similar 

 age in other parts of the Americas and in Europe. Hamilton (1953) assigned 

 ages to fossil foraminiferal oozes from Central Pacific seamounts on the basis 

 of planktonic species; and in correlating the New Zealand Upper Cretaceous and 

 Tertiary stages with the international time scale, Hornibrook (1958) based his 

 interpretations largely on planktonic Foraminifera. Monographic regional 

 studies of fossil reioresentatives of planktonic foraminiferal genera, such as those 

 of Subbotina (1953) on Russian globigerinids, hantkeninids and globorotaliids, 

 will enhance their applicability of inter-regional correlation. When a series of 

 Oligocene and Miocene radiolarian assemblages from the tropical Pacific floor 

 required correlation with a sequence of known age on land (Riedel, 1959a), 

 comparison of the associated foraminiferal assemblages with those described 

 from the Caribbean region provided an important part of the basis for the 

 correlation. The pre-eminent position of the Foraminifera in the sphere of 

 Tertiary inter-regional correlation is due largely to their frequent occurrence in 

 a great variety of sediment types in many localities, and to the intensity with 

 which they have been investigated. It seems that the only group which may in 

 the future challenge their position in this field are the coccolithophorids, which 

 apparently present a greater variety of widely distributed species, but which 

 have hitherto received little attention from stratigraphic niicropaleontologists. 



E. Pteropods 



Shells of these organisms can to a very limited extent be applied to problems 

 of age determination. They proved to be of assistance to Putsch (1934) and 

 Stainforth (1948) in their correlation of Tertiary molluscan assemblages of the 

 Caribbean region with those of Europe. 



F. Fish Debris 



Since the time of the Challenger Expedition (Murray and Renard, 1891), it 

 has been suspected that some of the sharks' teeth dredged in areas of slowly 

 accumulating red clay are Tertiary in age. In the present context, however, 



