28 
wrinkled scales and with teeth of uniform size form the genus Holoptych- 
ius, while Ehizodus contain those species, mostly carboniferous, having the 
scales thick and not wrinkled, and with teeth of two different sizes in the 
same jaw. The great laniary teeth of the latter equal in size those of 
the largest living crocodile and contrast strangely with the small ones at 
their side. There are four or five of these in each jaw and they strongly 
exhibit the peculiarities of the sauroid fish in their deeply fluted base, and 
the conical hollow at their root Their section is elliptical with a sharp 
cutting edge in front. The form of the fish is quite unknown, jaws and 
teeth being the only remains discovered. 
II. 
On some Gravels in the Valley of the Thames in Berkshire. 
By E. W. Claypole, B.A., B.Sc. 
Read at the Sectional Meeting, Match 7th, 1871. 
[Abstract.] 
The table land of the Midland counties of England down the gentle 
eastern slope of which the Thames has cut its channel consists of the soft 
secondary rocks, the Lias, Oolite, Greensand, and Chalk, in succession. The 
Thames therefore takes an upward stratigraphical course and flows 
continually into newer and newer formations. Its tributaries,, too, 
especially the upper ones, the Windrush, Evenlode, Cherwell, and Thame 
on the left bank, and the Kennet on the right, pursue a similar course 
and end in strata newer than those in which they rise. 
The gravel beds about to be described lie in that part of the Thames 
valley situated where the river crosses the long narrow belt of chalk 
which, like the other secondary strata traverses England from north-east 
to south-west, and in the neighbourhood of the town of Wallingford. 
This ancient borough stands on the left bank and in the hollow of the 
chalk along which the river flows. The breadth of the valley in this 
locality is from one to several miles, measuring from the Chalk Downs on 
one side to those on the other. The slope is usually gentle on both sides. 
The tops of the hills consist of the upper white chalk with flints, and their 
bases of the lower chalk or the chalk marl. The former, a pure carbonate 
of lime, graduates slowly and imperceptibly down into the latter, less white 
