312 MK. F. W. HAEMER ON THE LENHAM BEDS [Aug. 1898^ 



deposition of the Coralline Crag, still survived in the older Pliocene 

 seas (Piacentian) of Southern Europe/ The Pliocene deposits of the 

 Mediterranean thus represent, in a sense, an older fauna than do- 

 those of similar age in the Anglo-Belgian basin. Now, not only 

 do the Lenham Beds contain a somewhat larger percentage of 

 extinct species, but they are more closely connected with the- 

 Miocene on the one hand, and the Pliocene of the Mediterranean 

 on the other, than is the Coralline Crag, as shown by the following 

 numbers : — 



Species Occiirring in In the Pliocene 



still Miocene of the 



existing. deposits. Mediterranean .- 



Lenham 57 per cent. 75 per cent. 72 per cent. 



CoraUineCrag... 61 „ 59 „ 61 



These three independent methods of testing its fauna agree in 

 indicating that the Lenham Beds are older than the Coralline Crag. 

 In the foregoing comparison I have taken only the more abundant 

 species of the latter. If the rarer forms had also been included, the 

 difference between the two deposits would have been still greater. 

 The list of Lenham moUusca is not likely to contain any but species- 

 which are more or less characteristic. 



The view that the Lenham deposit is older than the Coralline 

 Crag seems to be confirmed by a more particular examination of its 

 molluscan fauna. In addition to the species enumerated in the pre-^ 

 ceding table (p. 311) we find at Lenham the following similarly 

 characteristic Miocene or Italian Pliocene forms, namely : — 



Fusus lamellosiis, Bors. I Cancellaria contorta, Bast. 



Pyrula reticulata, Lam. | Hinnites Cortesyi, Defr. 



These occur but rarely in the Coralline Crag, and were probably 

 beginning to die out in the Anglo-Belgian area during its deposition. 

 There is one species, however, Area diluvii (which Mr. Held informs- 

 me is one of the most abundant Lenham fossils), the presence of 

 which at that locahty is specially significant. This mollusc, widely 

 diffused during the Miocene epoch, and very common in the Bolderien 

 of Belgium, seems to have disappeared from the North Sea before 

 the Coralline Crag period,"- no trace of its existence having been 

 met with either in that formation or in any of the Diestien deposits- 

 of Belgium or Holland, but it still continued to inhabit the Medi- 

 terranean during the Pliocene era, as it does to this day. 



Another species, CarcUum papillosum^ may be also mentioned. 

 This Miocene and southern form, existing in the Mediterranean 

 both in Phocene times and at present, is unknown from any of the 

 Pliocene deposits of Belgium or East AngKa,but it is one of the most 

 abundant Lenham fossils. It may be noticed, on the other hand, that 

 the different species of Astarte, which occur in the Coralline Crag in 



' As the climate of the Pliocene period changed, certain species died out, but 

 they continued to exist longer in southern than in northern latitudes. 



^ Area diluvii is said hj MM. Viellard & Dollfus to occur, but only in 

 the oldest portion of the Pliocene of Normandy, ' Etude Greol. sur les Terrains- 

 Cret. et Tert. du Cotentin,' Caen, 1875, p. 151. 



