PRESTWICH — WOOLWICH AND READING SERIES. 133 



mottled clays, which now prevail exclusively, are perfectly barren ; 

 and the contrast which they afford with the common occurrence of 

 organic remains in the field we have just quitted is very striking, — 

 the more so from the circumstance of the unfossiliferous masses pre- 

 ponderating so largely, and the fossiliferous beds being confined to so 

 comparatively small an area of the Woolwich and Reading series. 



It is this Woolwich and Reading series which, of all the Lower 

 Tertiaries, presents the greatest resemblance in France and England. 

 The mottled clays of Paris and Montereau are not to be distinguished 

 from those of Reading and Newbury, whilst the Melania inquinata, 

 Nerifina globulus, Melanopsis buccinoides, Ostrea Bellovacina, Ce- 

 rithium variabile, and Cyrena cuneiformis, constitute at Epernay, 

 Soissons, and Dieppe, as at Woolwich and Upnor, the common and 

 characteristic species of the fluviatile and estuarine areas of this 

 period. 



The total number of Molluscs found in the " Woolwich and Read- 

 ing series" amounts to 53, of which 25 are peculiar to it, whilst of 

 the remaining 28 species 12 are found in the " Thanet Sands," 22 

 range up into the " Basement-bed of the London Clay," and 6 are 

 common to the three divisions. Again, taking these three divisions 

 of the "Lower London Tertiaries" together, the species of fossil 

 shells now enumerated from them amounts to as many as 82, of 

 which 29 are found in the " Basement-bed of the London Clay," 

 23 in the " Thanet Sands," and 53, as mentioned above, in the 

 Woolwich and Reading series*. Further, of these 82 species 27 range 

 up into the London Clay, and 6 have a further extension upwards 

 into the middle Eocenes, whilst 55 species are peculiar to these 

 Lower London Tertiaries. A fauna of this class and of this extent 

 (and which I believe is yet far from being fully worked outf)} in 

 addition to which there is to be noted a not inconsiderable list of 

 Entomostraca, Foraminifera, and Plants, entitles, I consider, these 

 Lower London Tertiaries to a more important and independent posi- 

 tion than has hitherto been assigned to them. 



* A further examination of some of the species enumerated in my lists of fossils 

 of the Basement-bed of the London Clay and of the Thanet Sands, has shown the 

 necessity of an alteration in the determination of some of the species which were 

 then identified with known species of some of the more important overlying 

 Eocene deposits ; amongst these there will be found in the first-named list 

 (Journ. Geol. Soc. vol. vi. p. 281, Table A.) the species given in the first column; 

 the second column gives the corrections. 



Corbula revoluta, Sow. "1 ^ „ „ . . , . „ „ 1 1 n\ 



, . » ■ ri J. r C. jReoMwzeraszs (see note c, p. liy). 



longirostns. Desk. J " ^ > r / 



Cyrena obovata, var. Sow. C. cordata (note d, p. 119). 

 And in the second hst (Journ. Geol. Soc. vol. viii. p. 248), — 



Dentalium nitens, Sow. 

 Corbula, as above. 

 Cytherea orbicularis, Mor. 



This identification is doubtful. 



C. Bellovacina, Desh. 



t In addition to the above there are about 20 to 25 specimens of apparently 

 new species, but not in a state sufficiently perfect to determine. 



