Vol. 52.] A DELIMITATION OF THE CENOMANTAN. 137 



but rather pieces of Pecten, fragments of the tests or spines of 

 echinodermata, polyzoa, and perhaps coral. 



Foraminifera are not uncommon, the genera represented being 

 chiefly Textularia, Cristellaria, and Motalia; Globigerina is rare 

 or absent, and calcareous ' spheres ' do not occur at all. Although 

 free sponge-spicules are uncommon, there is much sponge-structure 

 (? of calcisponges). 



Bed 11. 



Bed 11 resembles the finer and more shelly portions of Bed 10, 

 and specimens from Hooken Cliff, Beer Head, and elsewhere present 

 the same character. Like Bed 10, it consists of calcareous particles 

 derived from various sources, foraminifera, sponge-spicules, with 

 many quartz- and glauconite-grains, the latter being more common 

 than in Bed 10. The whole is cemented together by crystalline 

 calcite. 



Bed 12. 



This bed is a dense, hard, crystalline limestone, with smooth 

 fracture, containing many grains of quartz and glauconite, those of 

 glauconite being still more abundant than in Beds 10 and 11. 



Examination of thin slices proves it to be a true chalk, having a 

 matrix of fine, amorphous, calcareous matter, now converted into 

 granular calcite, in which are scattered a few shelly fragments, 

 foraminifera, and some sponge-spicules. Spheres are common — 

 the general aspect being that of certain specimens of Chalk Marl or 

 Grey Chalk. But the rock in other parts contains many coarse 

 shelly fragments and large glauconitic grains ; these areas, though 

 well defined, are not sharply marked off, and seem to be integral 

 portions of the rock. 



Bed 13. Hooken Cliff. 



The structure of Bed 13 seems to vary at different places, but 

 more examples are necessary to make sure of this point. The type 

 may be taken as the marked zone of Belemnitella plena at Hooken. 

 Here the matrix consists of fine amorphous calcareous matter and 

 minute calcitic crystals. A few coarse fragments occur which can 

 be identified as shell, and spheres and small-sized foraminifera are 

 common. The feature of the rock is the abundance of large angular 

 and rounded quartz-grains, and large grains of glauconite. The 

 whole is loosely compacted, and forms a friable gritty stone. 



The lower part of this bed has a somewhat different aspect. It 

 is a compact glauconitic chalk, full of quartz-grains and coarse 

 shelly fragments ; variety of structure in the latter indicates deri- 

 vation from various sources. A specimen supposed to be 13, from 

 between Lyme Begis and Pinhay, shows a structure which ap- 

 proximates to that of Bed 14 — the glauconitic base of the Middle 

 Chalk 



