STRATIGRAPHY OF THE CRAG. 87 



from Sutton, zone f. Spirillina vivipara, usually a rare species, is somewhat 

 common here. 



Zone g. — The most striking feature of this zone is the comparative abundance 

 of Lagense, particularly the marginate forms. Other rather common species are 

 Nonionina scapha, Spirillina vivipara, Miliolina oblong a, Planorbulina mediterra- 

 nensis, Textilaria sagittula, Bolivina Mnariensis, and Botalia Beccarii. 



Zone h. — This has not been examined for Forarninifera, as it is in all probability 

 part of zone g reconstructed. 



7. Aldbokough. — Zone g. The pits near the Red House, Leiston Road, close to 

 Aldborough, show about eight feet of fine buff-coloured rubbly limestone full of 

 Bryozoa, in part decalcified. Mollusca are not abundant, those species of which 

 the tests are formed of aragonite having been removed by percolation of carbo- 

 nated waters. Chlamys opercitlaris is abundant, however, as the shell consists of 

 calcite. 1 Owing to this decalcification Foraminifera are somewhat scarce in this 

 locality, only a few much decomposed Porcellaneous forms, such as Miliolina 

 oblonga, M. seminulum, and Biloculina ringens occurring. The Hyaline forms, 

 although better preserved, are usually in a somewhat decomposed condition, with 

 the chambering obscured. The list, therefore, in all probability by no means 

 represents the Foraminiferal fauna as originally existing. 



8. Sudbourne. — Zone g. Pits to the north of Sudbourne Church. 



The upper beds in this neighbourhood, nearly all referable to this zone, are 

 highly ferruginous, and prove to be very poor in Foraminifera. Certain species 

 are numerically plentiful, but all are difficult to determine, being coated with 

 oxide of iron in such a manner as to render the chambers and sutures indistinct. 

 The following is a complete list of species found after a long search : 



1. Polymorphina gibba, m. R. 



2. Olobigerina bulloides, m. RC. 



3. Planorbulina mediterranensis, m. R. 



4. Truncatnlina Ungeriana, s. RC. 



5. — lobatula, m. VC. 

 (3. — variabilis, m. VR. 

 7. Pulvinulina repanda, m. R. 



1 For an account of the experimental evidence obtained as to the cause of the inferior stability of 

 aragonite fossils as compared with those formed of calcite, with special reference to the Foraminifera 

 and Mollusca, see " On the Mineralogical Constitution of Calcareous Organisms," by V. Cornish and 

 P. F. Kendall, ' Geol. Mag.,' new series, dec. 3, vol. v, 1888, pp. 66—73. 



