To these Prof. Rupert Jones has added Polystomella striatopunctata, and a Cythere, sp. nov. (?), but related to some known forms.

A curious feature in this old beach is the occurrence of thousands of the tiny Cyamium minutum. This species is "gregarious among seaweeds and under stones at low water," and "has a high northern range; but its southern distribution is limited "*. The other species are common on the western coasts of Europe, and inhabit the littoral zone. They are all to be found, with one exception, in Mr. Damon's list of the shells of the Weymouth coastt.

The beach on the west cliff is very thick and massive, but contains very few shells. Mr. E. Cunnington, who was with me in 1863, found one specimen of Buccinum undatum, var.; and I obtained a few fragments of Mytilus; but we found no others.

The shingle of the raised beach is composed, in great part, of chalk flints, with which are mixed some pebbles of the harder beds and of the flint of the Portland rocks, together with others of a more distant origin, the following being the order of relative frequency and character of the pebbles forming the shingle, with the source whence they are derived :

1. Subangular fragments of flint.......
2. Chert.....

3. Ferruginous grit and sandstone..

4. Hard sandstone

5. Red and purple sandstone

6. Grey and red quartzite pebbles

7. Dark-red porphyry with large crystals of felspar

8. Light-red porphyry with small ditto...

9. Micaceous sandstone

10. Light-red granite.

Chalk.
Upper Greensand.
Lower Tertiaries.

New Red Sandstone and its conglomerates.

Devonian?

Cornwall?

With these I found on the east side two large boulders, one of which might be referred to a Tertiary sandstone, and the other to the Calcareous Grit.

Deposits over the Raised Beach.

At the Bill the raised beach caps the cliff, and is not covered by any other deposit, or only by a broken local débris; but as we trace

Fig. 2.-Section on top of cliff near the Boat-haul, Bill of Portland.

d

Angular rubble, d, overlying
and mixing with the raised
beach, e.

*

Portland beds.

Jeffreys's 'British Conchology,' vol. ii. p. 261.

† Op. cit. p. 175.

the beach to the northward, we find it passes under a light-coloured loam with seams of angular débris, succeeded by a mass of angular débris, chiefly of the local rocks (fig. 2).

On the east cliff the relation of the several deposits is not well shown. Still the order of succession is sufficiently apparent, and near the Sand-holes the section is as under (fig. 3).

Fig. 3.-Raised Beach, with overlying angular land-débris, loam, and sand, near the Sand-holes, east side of Portland Bill.

It is, however, on the west cliff that the finest section is exposed. Proceeding north-westward from the Bill, the beach is seen to pass under the loam with the overlying rubble-bed before mentioned. The loam varies in thickness from 10 feet at the northern end, to nought at its southern end, and contains subordinate seams of the same angular débris, giving it an appearance of rough stratification. In this loam I found, in places, seams containing considerable numbers of land and freshwater shells, but only of the few following species (determined, with the others, by Mr. Gwyn Jeffreys):

1. Limnæa peregra, Müller.

2.

- truncatula, Müll., var. spira producta.

3. Limax agrestis, Linné (shields). 4. Succinea oblonga, Draparnaud. 5. Pupa marginata, Drap.

I found only one small fragment of bone, and derived (Jurassic?) specimens of a species of Cythere.

But the most interesting part of the section is that exposed just beyond the point to which the quarrying has been carried, and where the beach ends by the side of a large fissure which runs inwards from the shore.

On the surface there is nothing to indicate any change, the ground continuing its gradual slight slope from north to south. Descending,

however, down the cliff to where the rock has been quarried near the fissure, the old beach, covered by the light-coloured loam, is found to abut against an old cliff of Lower Purbeck strata, the upper part of which is doubled back, and its débris thrown over the loam and carried southward, as shown in the following section (fig. 4).

Fig. 4.-Section of Raised Beach and Old Cliff at the top of the present cliff on the west side of Portland Bill. (See also Sect. 4, Pl. I.)

d. Angular débris, 4 feet. d'. Light-coloured loam with seams of débris and angular blocks; land and freshwater shells in places: 11 feet. beach with very large pebbles at base, 7 feet.

e. Raised

This overlapping mass of débris extends all over the line of old cliff, which it has levelled with the surface from this point to its termination near the Sand-holes on the east cliff. To the southward it gradually thins out as it recedes from the old line of cliff, and ranges seaward over the old beach; but still it is clearly traceable in places as far as the land-mark at the extremity of the Bill, where it mixes with the upper part of the old beach.

This bed of rock-débris is remarkable from the circumstance of its containing, with specimens of the unfossiliferous beds of the Lower Purbecks of Portland, abundant fragments of the fossiliferous beds of the Middle Purbecks, none of which now exist in situ in the island. In it I also found a number of fragments of the thin seams of fibrous carbonate of lime (known by the quarrymen as "beef"), and of the so-called cinder-bed, which consists of a concreted dark mass of small oysters (so common in the Lulworth and Upway Purbecks), Portland flint, fossil wood, and Tertiary iron sandstone. Mr. Etheridge has kindly determined for me the following species* :

* My friend Mr. Osmond Fisher, who was there with me, considers they may

Cyrene media.
Physa Bristovii.
Hydrobia.

Planorbis.

Cypris striato-punctata. legumen or fasciculata.

This mass of débris is angular or subangular, and is little or not at all worn-weathered only. It is not stratified, but roughly spread out with thin intercalated irregular seams of the same loam as d'. The loam itself shows traces of rough stratification, and contains thin lenticular seams of the angular débris, indicating the one and the other to be phases of the same phenomenon.

Near where the loam and rubble thin out is another feature which deserves notice. The old beach is here a loose shingle, and has been worked and removed over a considerable extent. This cleared

area presents, however, a series of low ridges or walls, running nearly north and south, which have been left by the workmen. On examination these are found to consist of the loam and rubble beds, d' and

Fig. 5.-Section showing the longitudinal breaks caused in the old beach by fissures filled by land-materials from above, but open below; Shingle-pit, between section 4 and the landmark.

Underground section, only posed in the cliffs to the southward.

V

f

1. Purbeck beds. 2. Portland rock. d. Soil and dark loam, with angular fragments. '. Loam, laminated. e. Raised beach. f. Open fissures. d, which have replaced the shingle. The cause of this is not difficult to find. On prolonging these loam-ridges to the edge of the cliff further southward, I invariably found them to correspond with one of the many lines of fissuret by which the island is traversed from

be referred to Nos. 57, 70, 77, and 82 of his section of Ridgeway (see Damon's Geol. of Weymouth, p. 107).

+ These fissures follow the lines of joint, which run within a few degrees on either A N.-and-S. fissure side of N. and S., and, with the same variation, E. and W.

will sometimes pass into one E. and W., and afterwards resume its first direction. They are not caused by an outward, or seaward, slip over the Kimmeridge Clay; for the beds dip slightly inwards, or inland, forming a shallow synclinal running N. and S. along the centre of the island. In the above section (fig. 5) the lower part of the débris above ƒ is represented too fine: it consists of large and small angular blocks of Purbeck and Portland beds.

south to north, and of which the fissures discovered in digging the Verne moat are an example. These fissures (f, fig. 5), which are from 1 to 10 feet wide, are generally open at bottom, while the top has been blocked up with débris of the upper strata, and, in this case, of the beds overlying them also. At Portland Bill blocks of the fissile Purbeck beds have been let down to a greater or lesser depth until stopped by the narrowness of the passage: the shingle bed, e, has fallen upon the rock-débris; and the loam bed, d', has followed on the shingle, forming vertical seams which, when the shingle came to be quarried, were left in ridges over the rectilinear fissures, as shown in the preceding section (fig. 5).

None of this angular rubble and loam exists in the centre of the island; but at the northern extremity of Portland there is a remarkable mass of it, though under very different conditions from that at the Bill. The high escarpment which ends abruptly above Chesilton is subtended at its base by a low cliff, which overhangs the southern extremity of the Chesil Bank for a short distance. This cliff, which rises to the height of 60 feet, is composed entirely of angular débris with sand, derived from the Purbeck beds and Portland Stone and Sands, spread out in great lenticular masses, and interstratified with

Fig. 6.-Old land-débris, with large boulders and seams of Loess, with land shells (at s). Cliff, Chesilton.

K. Kimmeridge Clay. irregular beds of loam, 1 to 4 feet thick, in places having the character of loess (fig. 6). The upper 6 to 10 feet consists almost entirely of broken Portland flint. Scattered through the mass of débris are large angular blocks of Portland Stone and Portland flint or chert, often several tons in weight. The rough bedding is in general slightly

*The following is the measurement in feet of some of these blocks:-9x8x31, 10×6×2,8x7×2, 3×2×1 feet. The last is of Portland flint, the others of Portland Stone. Mr. Fisher has since found in it a small block of Sarsen stone (? from the Portland drift).