268 Prof. Morris — Boring Mollusca in Oolites. 



species of Polyzoa and of Serpula, to those -which incrust the 

 separate plates and joints of the Apiocrinus rotundus, which occur 

 in the Bradford-clay at Bradford, Wiltshire. 1 .Coarse shelly lime- 

 stones, more or less irregular and false-bedded, with partings 

 of clay full of fossils; among the most common are Terebratula 

 digona, Lima cardiiformis, Pecten vagans, Ifodiola imbricata, Ostrea 

 Marshii, 0. Sowerbyi, Trigonia, Corbula, Nucula, Area, Serpula, 

 spines and plates of Echini (AcrosaJenia and Cidaris), Corals (Clado- 

 phyllia Babeana), Bhynchonella media, Cerithium, Cylindrites, Nucula, 

 and fragments of wood. 



Below is a laminated grey and brown clay with shells, overlying 

 a thick-bedded, hard, grey, fine-grained rock, destitute of fossils, a 

 highly siliceous and calcareous rock, with thin flagstones in the 

 middle ; the rock is used for road stone. 



Professor Church has kindly examined this stone, which, when 

 perfectly dry, was found to contain 39 per cent, of silica. 



The perforated nodules above mentioned evidently show a change 

 of condition from the underlying bed, and probably infer not very 

 deep water, in which a partially hardened mud was broken up into 

 separate pieces which were subsequently perforated by the Litho- 

 domous mollusc. Some movement must have taken place in their 

 position, for it is observed that both the upper and under surfaces 

 are equally bored and the sides also : rarely do the borings interfere 

 with each other, and they are generally of a uniform size about an 

 inch deep ; further evidence of comparatively quiet conditions is 

 exhibited not only in the perforations, but in the surfaces of the 

 nodules being frequently more or less covered by the attached valve 

 of oysters and a carinated Serpula, as well as incrusted with a 

 species of Diastopora or Berenicea, showing a period of repose 

 between the underlying and overlying strata, in which the false- 

 bedding is seen. 2 Similar perforated pebbles have been observed in 

 the cutting of the Oolite on the Bailway, near Long Handborough, 

 Oxfordshire. 



Prof. Phillips, in describing the section of the large old quarry 

 opened on the west side of the Cherwell, at Enslow Bridge, shows 

 that immediately below the strata referred to, the Forest Marble, is a 

 white and partly compact Oolite in three or four beds, the top being 

 ferruginous, often covered by Oysters, and drilled by Lithodomi? 



The Bev. H. Jelly mentions, that " in the superior members of the 

 Great Oolite formation in the neighbourhood of Bath there occur 

 masses, sometimes of considerable size, of Astrece, perforated most 



1 See fig. 338, p. 330, Lyell, Elements of Geology, 1874. 



2 Sir C. Lyell, in alluding to the Crinoidal plates at Bradford, overgrown with 

 Serpula and Polyzoa, says, " Now these Serpula could only have begun to grow 

 after the death of some of the stone-lilies, parts of whose skeletons had been strewed 

 over the floor of the ocean before the irruption of argillaceous mud. In some in- 

 stances we find that, after the parasitic Serpulce were full grown, they had been in- 

 crusted over with a polyzoan, called Diastopora diluviana ; and many generations of 

 these molluscoids had succeeded each other in the pure water before they became 

 fossil ! (Elements of Geology, 1874, p. 330.) 



3 Geology of Oxford and the Valley of the Thames, 1871. 



