54 
THE GEOLOGIST. 
In addition to the fossils mentioned above, I have collected from these 
" pebble-beds " specimens of the teeth of — 
Sanrichthys apicalis . . ^ 
^. Mongeoti | Fossils of the Trias of Ai;st chff and 
Hyhodus Minor \ \ \\ bone-bed at Axmouth. 
Acrodus minimus . . .) 
f Sr;"'"'''' ; : } °f 
H. grassiconus. 
S. 1 
Lepidotus (two or more species in abundance). 
Sphcerodus ? 
Gyrodus. 
Fycnodus Mantelli. 
Acrodus. 
Strophodus 1 
Lamna longidens. 
Notidans. 
and some others. The greater number of these specimens are more 
or less broken ; yet many of them are by far too perfect and delicate to 
have been drifted from a distance. I have also, from the same deposits, 
casts of about thirty species of small univalve and bivalve shells, -n hicb, 
at present, I have had no opportunity of identifying. 
The ''pebble-beds," therefore, appear to offer double evidence in regard 
to this " old ridge : " firstly, in affording a proof of its existence as a 
coast-line ; and secondly, in pointing out a time of its partial submergence : 
"with the latter evidence I have now to do. 
A thin stratum of sand, clay, and pebbles (described by Fitton as a 
" kind of gravel "), occurs at the base of the Lower Greensand, at its junc- 
tion with the "Wealden. Again, the basement-bed of the Gault, as at Eed- 
cliffe, contains numerous subangular pebbles. In both of these cases the 
pebbly strata represent a change in the relative level of laud and water, 
sufficiently extensive to have altered the character of the succeeding de- 
posits ; and thus it seems probable that the " pebble-beds " at the base of 
the upper division of the Lower Greensand represent a similar disturbance ; 
the effect of which, I think, may be easily traced. 
Ko Greensand deposits older than the upper" or ferruginous division of 
ritton are found to the west of a line drawn from "Warminster to the Isle 
of Purbeck, or north of a line passing from Dover, through Eochester, 
Croydon, Kingsclere (Hants), and then on to AT arminster, or, in other 
words, north of Godwin-Austen's "old ridge." Greensand deposits, however, 
corresponding to Fitton's upper division, are found greatly to exceed these 
limits, both on the north and est. It appears, therefore, to be tolerably 
certain that the " pebble-beds " at the base of the ferruginous division re- 
present, and are the immediate result of, a period of considerable depres- 
sion, during which the Lower Greensand ocean extended itself far to the 
northward, across a portion of the " old ridge," and westward into Devon- 
shire. By supposing this ridge to have been cut through or partially sub- 
merged at this period, one difficulty, at least, as regards the " pebble-beds," 
will be done away with — viz. that of the occurrence in one stratum of the 
fossils of several separate formations. For, supposing such a ridge to have 
existed as a land-surface from a period prior to the deposition of the Lias, 
every succeeding deposit must have been brought up against it, as has 
been suggested by Air. Austen ; and, consequently, an oceanic current, in 
