106 Lankester— Crag. 
there are gaps where strata are wanting; and very rarely do the 
various beds rest conformably one on another. 
Overlying the Rupelian or Eocene Clay, above mentioned, which 
is rarely exposed in the diggings, is a fine black sand, enclosing a 
very great number of fossils, which have a grey tint. All the Shells 
contained in this bed are perfect, many heing closed Bivalves; the 
stratification is very even; and altogether the sand bears indication of 
having been quietly deposited. The immense abundance of the valves 
ofavariety of Pectunculus glycimeris, a common fossil of the Coralline 
Crag, and represented by a noticeable variety (swbobliquus) in the 
Red, is truly surprising; in fact, I have never seen so many Oyster- 
shells in a fishing-town, as I saw Pectunculi here. Venus casina, 
Cardita senilis (?), Astarte, Nucula, and a Volute, somewhat simi- 
lar to Voluta Lamberti, are amongst the most conspicuous Mollusca ; 
while Natice, Pleurotome, Scalarie, Fusi, and others, are not un- 
common. With these is associated a beautiful Coral, of the genus 
Stephanophylla, as well as Polyzoa (Lunulites, Flustra, and others). 
The Black Crag occupies by far the greater extent of the fortifica- 
tions, in the formation of which many new species have been dis- 
covered. Above the Black or Lower Crag exists a bed of fine green 
sand, generally unfossiliferous, more particularly developed on the 
southern side of the works. In certain spots, however, a new species 
of Ostrea and a Terebratula, which may perhaps be considered as a 
variety of the well-known 7. grandis, variabilis, spondyloides, vel 
Sowerbii, are found, as well as a few fossils of the Black Crag. This 
bed must therefore be regarded as a member of the Lower Crag ; 
the change in its paleontological aspect resulting from some corre- 
sponding alteration of the level of the sea-bottom. Succeeding the 
green and black beds, is a grey bed, containing fossils of a much 
more recent aspect than most of those of the Black Crag, and there- 
fore considered as a distinct deposit. This Middle Crag contains 
Cyprina rustica, Astarte Omalii, and numerous unrolled and well- 
preserved Cetacean remains and teeth of Sharks. Above this 
comes a yellowish-brown argillaceous deposit, of considerable 
thickness,* containing fossils of yet more recent form. 
The yellow or Upper Crag contains Cyprina rustica and Pecten 
maximus abundantly, Astarte mutabilis, Cyprina Islandica, Nassa 
labiosa, Lingula Mortieri, and Voluta Lamberti of the typical 
form, also Cetacean and Fish-remains. The teeth of a species of 
Phoca have been described by M. Van Beneden from the Upper 
Crag also. Above the Upper Crag is a Pleistocene deposit, which 
forms an excellent parallel to the Pleistocene beds capping the Red 
Crag of Suffolk —( To be continued.) 
* It is impossible to estimate correctly the depth of any of the strata, as the 
trench varies much in depth itself. It is in most places 9 metres (293 feet) ; 
and a glance at the section will show the relative amount occupied by each bed. 
