BENSTED — ON THE GEOLOGY OF MAIDSTONE. 
447 
are obscurely marked by a few longitudinal ribs. The beak is somewhat produced, in- 
curved, and truncated by a small foraminal aperture, which is separated to some extent 
from the hinge-line by a deltidium. The dorsal valve is not nearly as convex as the ven- 
tral one, and is likewise divided into three portions, the central one being flattened and 
furrowed by four longitudinal ribs, while the lateral portions become more elevated as 
they approach the front, and curve inwards so as to meet the valve-edges of the central 
lower portion of the valve. 
Upon each of the lateral portions of the valve may be observed six or seven ribs, which 
become somewhat obscured as they approach the margin of the shell. Interior un- 
known. 
Length, 1 inch 7 lines ; width, 1 inch 3 lines ; depth, 10 lines. Tertiary, Malta. 
Ols. The recent species to which this shell bears the closest re- 
semblance is the Wo.ldheimia Jiavescens, Lamarck, now alive in myriads 
at Port Jackson, Au&tralia, as well as in some other localities. The 
recent species is however more regularly ovate than is the fossil one, 
the beak is less elongated, and with a larger foraminal aperture. 
THE GEOLOaY OF MAIDSTONE. 
By W. H. Bensted, Esq. 
{Concluded from page 382.) 
There only remains now to notice the post-Tertiary deposits to com- 
plete this account of the geology of Maidstone. The surface-soil 
and the earth filling in and covering over the faults and large fissures 
consist of clay, gravel, " sharp " drift-sand, and fine sand, all being 
sedimentary deposits from water under different rates of motion. 
The exteriors of the highest masses of rock show the eflTects of a 
powerful erosion continued for a long period of time ; but this action 
was not the dashing of billows, for some surfaces of the rock, although 
worn to a great extent, have portions of fragile shells standing out 
from their surfaces, just as in the cavernous gutters of the rock 
masses of spiculae jut out from the walls, the loose sand or soft hassock 
having been washed away. 
Old watercourses exist at a considerable 
depth from the surface, showing that a gra- 
dual lowering of the water-level of the springs 
has taken place. 
The opinion I have formed respecting the 
beds of drift and sedimentary clays, which 
^ ^ ^ '6 in the district are found between the masses 
Fig. 9. — Protrusion of Rag- of rock, is that an elevating force has lifted 
stone into Drift, a<^ Inlaid- these masses, bearing up the drift and clay 
stone. «, beds of Ragstone ; (pig. 9)^ and that, in some instances, the 
*/,dnft; c..c,clay;^a?, ^^^^ ^^^^-^^^ ^^^^^^ of rock have 
line 01 flints. f jii-, 1 ■> • 11 
been protruded into the driit and clay, 
piercing and dividing them into lines at angles parallel with their 
sides. 
