Vol. 6$.~] AND COEALMAN ROCKS OF BRILL. 33 



The following fossils were found in the limestone : — 



Pictonia cf. Cymodoce (d'Orb.). 

 ? Olcostephanus Berryeri 

 (Lesueur) — fragments seen. 



Pholadomya (squalls, Sow. 

 Pleuromya recurva (Phil.). 



3. — Below the limestones comes a thickness of about 8 feet of 

 dark-grey, brown-weathering clay, with occasional, small, black and 

 whitish-brown, phosphatic nodules, not exceeding 1 inch in greatest 

 length. This clay yielded only a few fossils : — 



Ostrea (deltoidea ? Sow.^l, frag- Ostracoda. 



ments. Crislellaria sp. 



Serpula sp. ? Botalia. 



2. — The selenitic clay which forms the lower part of the section 

 is the most interesting division. It is a shaly black clay, weathering 

 lilac-grey with sulphur-yellow stains, and showing a crumpled 

 lamination. It contains abundant crystals of selenite, of all sizes 

 from less than 5 millimetres up to about 20 centimetres in length. 

 These are mostly the normal combination (010, 110, Til), 

 untwinned, but a few show twinning, and a few show parallel 

 growth tapering in one direction. Only in one place have I found 

 a large mass of selenite (possibly an altered cement-stone) composed 

 of lenticular crystals like those described on p. 32 from a higher 

 horizon. In addition, selenite replaces, partly or completely, the 

 calcite of the abundant belemnites and, very rarely, that of oysters. 

 These latter fossils are abundant in an unaltered state. 



Such at least were the characters of this clay some years ago, 

 and they can still be seen in parts of the brickfield ; but, with the 

 cutting-back of the working-face farther into the hill, the selenite 

 has diminished in amount, while instead are seen its antecedents 

 in the form of crushed shells, ' race,' and (in washings examined 

 with a lens) abundant granular aggregates of pyrites (probably 

 marcasite) . 



The following fossils occur in this clay : — 



Reptilian bones. 



Belemnites abbreviates, Miller. 

 Belemnites nitidus, Dollf. 



(= B. explanatus, Phil.). 



Gryphma dilatata, Sow. 

 Ostrea deltoidea, Sow. 

 Exogyra nana, Sow. 

 Trigonia Voltzii, Ag. 

 Protocardia sp. (crushed). 

 Other crushed shells. 



The selenitization of the belemnites is a most interesting feature 

 of this clay. The belemnite-guards, some of which exceed an inch 

 in diameter, are usually changed completely into selenite, often 

 with many small crystals projecting from the surface and obscuring 

 the form, while the internal structure may be quite lost. In some 

 cases, the selenite-crystals preserve the radiating arrangement of 

 the original calcite ; and in parts of some specimens radii of 

 unaltered calcite may be seen alternating with others of selenite. 

 (PI. I, fig. 1.) In such cases, the concentric structure of the guard 



Q.J. G. S. No. 249. d 



