FOSSILS OF THE CHALK. 



385 



has been discovered in the oolite's, with the external sheath, 

 the conical-chambered shell, the ink-bag, and the bone ; the 

 ink, though fossilised, retaining its pigmentary property. 



The following figure (270) represents several of the most 

 characteristic fossil shells which are special to the beds 

 that underlie the white chalk, the marl, the gault, and 

 the upper greensand : 





FIG. 270. 1. Tnrrilites costatus (Chalk Marl). 2. Scaphites striatus (C. Marl). 

 3. Karaites (C. Marl). 4. Inoceraraus sulcatus (Gault). 5. Ostrea carinata 

 (Greensand). 6. Inoceramus concentricus. 



Dr. Fitton has published * an admirable memoir on the 

 Lower Greensand or neocomian strata of Atherfield. The 

 beds, 808 feet in thickness, contain 160 species of fossils, 

 the range and distribution of which the author has exhibited 

 in a tabular form ; it is impossible to employ terms of com- 

 mendation too high, in referring to this valuable memoir, 

 which, for clearness and accuracy, is a model for all geo- 

 logists: we give from Dr. Mantell's "Isle of Wight" the 

 annexed plates of the most characteristic shells of the lower 

 greensand, or neocomian strata. 



* Geological Journal, vol. tii., p. 289. 



CC 



