Page:Quarterly Journal of the Geological Society of London, vol. 31.djvu/80

34 34 J. PRESTW1CH ON THE QUATERNARY PHENOMENA To these Prof. Rupert Jones has added PolystomeUa striatopunc- tata, 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 coast f. The beach on the west cliff is very thick and massive, but contains very few shells. Mr. E. Cunniugton, 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. . . ., Chalk. 2. Chert Upper Greensand. 3. Ferruginous grit and sandstone 1 ^ TerU aHe S. 4. Hard sandstone J 5. Eed and purple sandstone ~j 6. Grey and red quartzite pebbles I New Bed Sandstone 7. Dark-red porphyry with large crystals of felspar f and its conglomerates. 8- Light-red porphyry with small ditto j 9. Micaceous sandstone, Devonian? 10. Light-red granite 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 Calca- reous 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 debris ; but as we trace Fig. 2. — Section on top of cliff near the Boat-haul, Bill of Portland. Angular rubble, d, overlying and mixing with the raised beach, e. ^ Portland beds. f Op. cit. p. 175.
 * Jeffreys's 'British Conchology,' vol. ii. p. 261.