TAB. XXV. 



Fig. 



1. Gastrana laminosa, p. 217. From Coralline Crag, Sudbourne. 



d, e, specimen distorted. From Red Crag, Walton Naze. 



2. Cultellus tenuis, p. 258. From Red Crag, Walton Naze. 



c, d, hinge of both valves slightly enlarged. 



3. Macha strigillata, p. 252. From Coralline Crag, Sutton. 



4. Pandora Pinna, p. 270. 



5. Pandora insequivalvis, p. 270. 



6. Solen ensis, p. 256. From Red Crag, Walton Naze. 



a d, various specimens showing different proportionate dimensions. 

 e,f, exhibit muscular impressions. 



7. Solen siliqua, p. 255. From Red Crag, Sutton. 



b, d, interior view, to show difference in muscular impressions. 



c, a small elongated specimen, with valves united. 



8. Solen gladiolus, p. 254. From Red Crag, Walton Naze.* 



* In support of the presumption assumed in th'e note at page 255, that the Red Crag is not wholly 

 derivative, it may be further remarked, that at the part of the cliff -whence this specimen was obtained, 

 there are no extraneous fossils whatever, at least none that I have been able to discover, which could be 

 decidedly said were foreign to the deposit. The shells here rest immediately upon the London Clay, and 

 are in the highest state of perfection ; not only are there many Bivalves in their natural position, but the 

 numerous specimens of the reversed variety of Trophon antiquum have the fragile apex or pullus seldom or 

 never removed. Many species are also found that are not met with in the Coralline Crag ; though this 

 latter evidence is not of itself conclusive, it helps to sustain the argument deduced from the perfection of 

 the specimens. The whole aspect of the Fauna at this locality differs from that of the White or Coralline 

 Crag ; the same also may be said of its lithological character, and, in my opinion, the probabilities are greatly 

 in favour of the Red Crag, certainly at Walton-on-the-Naze, being pure and genuine, and of an Age 

 geologically subsequent to the Coralline Crag. 



