STRATIGRAPHY OF THE CRAG. 81 



several species in localities or periods where they were before unknown. Thus, 

 in this presumably Pliocene deposit, we have forms which hitherto have been 

 known to exist only in Eocene or Miocene periods ; whilst, on the other hand, 

 there are several species which, now living in the seas in various parts of the 

 world, are here for the first time found fossil." 



To a certain extent this is undoubtedly true ; but making allowance, as we 

 should, for the difference of sea-bottom and the nature of each deposit — the St. 

 Erth fossiliferous bed consisting of a fairly pure clay, and the Coralline Crag of 

 Bryozoan and Molluscan detritus — we naturally expect to find considerable differ- 

 ences in the entombed organisms. We thus find a very rich assemblage of 

 Lagense in the St. Erth beds (thh'ty-six species), while but twenty-three are 

 recorded from the Coralline Crag, of which eighteen are common to the two. One 

 of the most interesting recorded is Lagena semi inula, Brady, a species only met 

 with at six stations by the ' Challenger,' two in the South Atlantic and four 

 in the South Pacific, with a range of depth from 1300 to 2350 fathoms. In the 

 St. Erth clay it is rare; but in the Coralline Crag at Sutton (Zone f) it is rather 

 common, so that we have in the Pliocene the earlier appearance of a comparatively 

 shallow-water form, which has since migrated to deeper seas. The Polymorphinas 

 so well represented in the Coralline Crag appear to be somewhat rare at St. Erth, 

 but of the fifteen recorded species ten are also found in the Coralliue Crag. 



Taken altogether, the balance of evidence, so far as the Foraminifera are con- 

 cerned, supports the arguments adduced by Mr. C. Reid for the inclusion of the 

 St. Erth Beds with the Older, rather than with the Newer Pliocene, as suggested 

 by Messrs. P. F. Kendall and R. G. Bell. 1 



As the scope of this Monograph is limited to the Foraminifera of the Crags of 

 the Eastern Counties, it is not proposed to further describe the St. Erth forms, more 

 especially as they have already been so ably dealt with by Mr. Millett ; and we 

 learn from him that " there are still many species undetermined, which will form 

 the subject of a concluding notice." The species common to the Coralline Crag 

 and St. Erth beds are tabulated in the Appendix. 



CORALLINE CRAG. — As it is from this division of the Crag deposits that we 

 have obtained by far the largest and best assortment of species of Foramiuifera, 

 its subdivisions will be more fully dealt with. 



Subsequent to the publication of Part I of this Monograph Professor Prestwiclr 

 published his researches on these beds, and subdivided the Coralline Crag into 

 several zones, to each of which he assigned an index letter. The total thickness 



1 For the relation of the St. Erth beds to those of Cotentin see C. Eeid, ' Pliocene Deposits of 

 Britain,' 1890, p. 67. 



2 J. Prestwich, "On the Structure of the Crag-beds of Suffolk and Norfolk." Part I. The 

 Coralline Crag of Suffolk," ' Quart. Journ. Geol. Soc.,' vol. xxvii, 1871, p. 115, et seq. 



