PLATE VII. 
Fig. 1. 
Melbourn Rock, Hitchin, Herts. 
The lower and whiter part. The rock at this horizon consists of 
extremely fine calcareous particles, presumably derived from shells, 
and of “ spheres.” Allowing for a little variation in the size and 
quantity of the shell fragments, as well as in the number and the 
definition in the outline of the “ spheres,” this is the type of chalk which 
occurs immediately above the zone of Actinocamax plenus over a very 
wide area. 
Fig. 2. 
Melbourn Rock, Hitchin, Herts. 
The upper yellow bed. In the upper part of the Melbourn Rock 
the shell fragments are very abundant and usually coarse. This type 
of chalk does not extend over so wide an area, and is confined to the 
Midland, Southern and South Eastern Counties, a. a a. a. coarse 
shell-fragments, nearly all derived from Inoceramus mytiloides , rarely 
an Echinoderm spine, plate, or ossicle occurs ; a few Foraminifera ; 
b. Gaudryina ; c. Globigerina. 
