1852.] 



BROWN — UPPER TERTIARIES AT COPFORD. 



189 



On this calcareous clay we have a very compact deposit of vegetable 

 matter (No. 3 of the section), generally from 3 to 12 inches thick, 

 but at the eastern section it increases northward to a thickness of 6 

 or 7 feet. It is similar to peat, but not so inflammable, having a small 

 portion of argillaceous matter distributed throughout its mass. It is 

 often incorporated with the upper portion of the blue clay. In this bed 

 have been found compressed branches of trees and shells of the Fal- 

 vata piscinalisy Sind in 1836 I found Cyclas rivicola in groups. 



Over this layer of vegetable matter there occurs a bed of shell-marl 

 (No. 2 of the section), from 1 to 6 feet thick, which lies conformably 

 on the undulatory surface of the blue clay, into which it sometimes 

 sends down oblique veins (west section) . This bed dips to the north 

 with a slight angle (about 5°), and thins out towards the southern part 

 of the brick-field. It varies considerably in its character throughout 

 this area, sometimes consisting wholly of a white calcareous marl, 

 having a chalky appearance, and sometimes of the latter alternating 

 with ferruginous sands, or passing into sand or clay. In the western 

 excavation it is chiefly composed of white sand and shell-fragments 

 {Valvata piscinalis). In the first-named condition, no shells or parts 

 of shells have been found in it, although most probably it is wholly 

 derived from the decomposition of accumulated remains of dead mol- 

 luscs. When it becomes sandy, however, both broken and perfect 

 shells are not rare ; but when it passes into clay, the remains of land 

 and freshwater molluscs are abundantly found in a perfect state. In 

 the light-coloured clay (2\ of the Section), into which the marl passes 

 in one part of the eastern section exposed in 1850, thirty-two species 

 have been found. 



List of Land and Freshwater Molluscs'^ from the Copford Shell- 

 marl (2 and 2* of the Section). 



Land Shells. 



Limax agrestis (W.).t 



carinatus (E.). 



Helix hortensis (W.E.). 



nemoralis (W.E.). 



arbustorum (W.E.). 



' hispida (W.E.). 



concinna (W.E.). 



pulchella (W.E.). 



fulva (W.E.). 



— - — fusca (E.). 



rufescens (W.E.). 



— — depilata (E.). 



aculeata (W.E.). 



lamellata (W.E.). 



incarnata ? (W.) (Extinct.) 



• sericea (W.). 



lapicida (W.). 



Helix ruderata (W.). (Extinct.) 



, ova of (W.). 



Zonites rotundatus (W.E.). 



radiatulus (W.E.). 



purus (W.). 



nitidulus (W.E.). 



pygmseus (W.E.). 



crystallinus (W.E.). 



cellarius (W.). 



alliarius (W.). 



lucidus (W.) , 



Bulimus obscurus (W.). 



acutus ? (W.). 



Azeca tridens (W.). 

 Zua lubrica (W.E.). 

 Pupa marginata (W.). 

 umbilicata (W.). 



* The nomenclature here used is that of Gray's * Turton's Manual,' in accord- 

 ance with which the shells were named when the collection was first formed. 



t W. denotes that the shell has been found in the western part of the field, and 

 E. in the eastern part. 



VOL. VIII. — PART I. O 



