G. E. Dihley —Chalk Rock in North Kent. 373 



thickness, at the floor of the pit. The upper limit of the bed passes 

 imperceptibly into the Holaster planus Chalk. 



At Blue Bell Hill this fauna can be collected from the Chalk, one 

 hundred yards from the summit (about 750 feet O.D.), at the sides of 

 the path immediately opposite the church, between the school and 

 the Windmill Inn. Most probably this bed crops out again in the 

 large pit at the top of Blue Bell Hill (No. 10), but the face of the 

 Chalk is too precipitous to allow of an examination. 



The following is the list of fossils found in this bed. With the 

 exception of the Echinoids and Brachiopods, most are preserved as 

 casts, and on the whole can be determined only by the taking of 

 gutta-percha moulds. 



Heteroceras reussianum (Orb.) ; Baculites bohemicus, Fritscli ; Ptychoceras 

 Smithi (Woods) ; Scaphites geinitzi; Hamites sp. (?), Orb.; Prionocyclus nephmi 

 (Geinitz) ; Dentalium turoniense. Woods ; Avellana sp., of. JiumhoUi, Miller ; 

 Trochus schluteri, Woods ; TrocJius berocscirense. Woods ; Lampusia (?) sp. ; 

 Turbo geinitzi,'Woods; Solariella gemniata {So'verhj) ; Trapezium trapezoidale 

 (Eomer) ; Septifer lineatus (Sowerby) ; Inoceramus costellatus, Woods ; 

 Inoceramus ijiconstajis, Woods; Limahila sp. ; Spondylus spinosus (Sowerby) ; 

 Liothyrina semiglobosa (Sowerby) ; Rhynchonella limbata (Schlotheim) ; 

 Bhynchonella plicatilis (Sowerby) ; Holaster planus, Mantell ; Mieraster prce- 

 cursor, Eowe ; Mieraster leskei, Desmoulins ; Parasmilia sp. ; Trochocyathus 

 sp. ; Sponges (abundant). 



Mr. H. Woods ^ proposed the term ' zone of Seteroceras reussianum ' 

 for this assemblage, and remarked that it was not always characterized 

 by its peculiar lithology. He mentioned Twyford, near Winchester, 

 as a locality where the horizon can be recognized only by its fossils. 

 In the present district also it is patent that since the Chalk Rock 

 {sensu sir.) is absent, the palseontological term is to be preferred for 

 denoting this horizon. A more general use of this term as an index 

 to the horizon is highly desirable, because, as Mr. Woods has already 

 pointed out, the terra ' Chalk Rock ' is both inadequate and in some 

 cases ambiguous. Owing to this bed being less conspicuous in its 

 lithology than usual, it is highly probable that a detailed examination 

 of the Chalk at this part of the Holaster planus zone may throw con- 

 siderable light on the persistence of this zone. 



We again visited the Borstal Quarry, recently, accompanied by 

 Mr. P. Dollman, and during seven hours' work succeeded in revealing 

 very important features after clearing a few yards of the surface. 

 About ten feet above the floor a band of deeply iron-stained, nodular 

 chalk is seen to be persistent throughout the quarry ; these nodules 

 are very hard and contain beautiful casts of Sponges, Lamellibranchs, 

 Gasteropods, and Cephalopods. Immediately below the nodular band 

 the chalk is decidedly soft, friable and somewhat gritty ; but portions 

 of the mass are very hard and not easily distinguishable by the eye 

 from the surrounding matrix. I have obtained three beautiful 

 examples of Scaphites geinit%i from this horizon, and we found 

 Mieraster leskei more frequently here than in any other part of the 

 quarry. 



The day previous to the visit to Borstal, we spent several liours at 



1 Q.J.G.S., vol. lii, p. 70, 1896. 



