546 1IESSE8. G. F, FEANKS A^-D J. B. HAERISON- [Allg. 1 898, 



limestone-rocks are almost wholly made up of them. On the eastern 

 spur of Bissex Hill and on the outlier towards Monkey Hill, the 

 gradual change of the Upper Globigerina-ma^vls into Amphistegina- 

 limestones, and from these, through basal reef-rocks having the 

 characters described by Mr. W. Hill,^ to true coral-rocks, is well seen. 

 The total thickness of the Glohigerma-msirls as exposed on Bissex 

 Hill is apparently about 90 feet ; that of the passage-rocks, from 

 the marls to the true coral-rocks, is very variable, but probably in 

 no case exceeds 20 feet. The following is a summary of the vertical 

 succession of the Globigerina-m.aiT\s and reef-rocks at this locality : — ' 



Reef-rocks : / 5. Coral-rock. 



20 feet. \ 4. Basal reef-rocks without coral. 

 r r 3. Giobigerina-marls, with many inclusions of Oceanic earths. 



-p . " J 2. Globigerina-m-drls with few inclusions. 

 •L^ J. QA f i. 1 1. Detrital beds of Globigerina-m-drl, with \ery many inclu- 



^ '' ' [ sions of Oceanic earths and at times of Scotland Clays. 



The Glohigerince of the Bissex Hill marls are characterized by 

 their considerable size, their robust, thick-walled tests, and in 

 these characteristics they resemble those dredged by the Buccaneer 

 in 1886 in the South Atlantic (lat. O'' 1' 8., long. 15° 56' 5" W.) from 

 a depth of 1845 fathoms. They are in marked contrast, in this 

 respect, to the small Glohigerince with thin-walled tests present in 

 the included fragments of Oceanic chalks. Their colour also is 

 different, being generally of a light buff, and at times they contain 

 glauconite ; those of the Oceanic earths usually have a glistening 

 white appearance. The Bissex Hill marls bear, however, a 

 remarkable likeness to the Glohigei-ina-iock figured by Alex. Agassiz.^ 

 This is said to be part of a slab dredged off Alligator Eeef at 

 147 fathoms, but no account of it is given, and we are therefore 

 uncertain whether it is derived from a recent deposit or from a 

 submarine outcrop of a rock such as the Globigerina-limestone of 

 Barbados. 



Apart from the foraminifera enumerated by Mr. Chapman (see 

 Appendix, p. 550), very few fossils have yet been found in the Bissex 

 Hill marls. The following short list includes all that are known, 

 and the sharks' teeth are by far the commonest among them : — 



' Carcharodon (teeth). 

 -rr , Hemivristis (teeth). 



VERTEBRATA < j /t. lx^k ' 



Lamna (teeth). 

 ^ Oxyrhina (teeth), 

 r ArchcBop7ienstes abruptus, Gregory. 

 Invertebrata -! Pentacrmus (single joints of stem). 

 [ Small turbinate corals (as casts). 



The Scalaria described by Sir E. Schomburgk as Sc. Ehrenhergii 

 and as having been obtained from Bissex Hill came very probably 

 from these beds, for he found it in a rock ' composed of yellow 

 siliceous limestone or calcareous freestone, in which some shells, 

 spines of Echini, and teeth from two species of sharks have been 

 found.' ^ 



1 See Quart. Journ. Geol. Soc. vol. xlvii (1891) pp. 246-247. 



2 'Three Cruises of the Blake' vol. i (1888) p. 265, fig. 182. 

 ^ Schomburgk's ' History of Barbados,' 1848. 



