Vol. 69.] TWO BEEP BORINGS AT CALVERT STATION. 315 



well- defined horizon. Taking this bed of green clay as a datum, 

 we found that in the borehole there is 14 feet 9 inches of grey 

 ■earthy and oolitic limestones between it and the Oxford Clay ; 

 while at Blackthorn Hill a thickness of 18 feet 3 inches is recorded 

 between it and the base of the Cornbrash : thus there is a 

 remarkably close agreement. Below the green clay at the latter 

 locality, however, the clays are only a little more than 3 feet 

 thick, whereas in the cores at Calvert 27 feet of clays are recorded. 

 Even allowing for all possible chances of error, by excluding the 

 limestones below the green band from the measurements, there still 

 remains a considerably greater thickness of clay. 



Excepting the highest bands of limestone, the Forest Marble is 

 fairly fossiliferous throughout ; but, as a rule, the forms are poorly 

 preserved. Some of the limestones are shelly, Ostrea appearing to 

 be plentiful in some beds ; but the fossils were difficult to extract, 

 owing to the hardness of the limestone. In the grey earthy lime- 

 •stones overlying the band of green clay Pteroperna costatula (Desl.) 

 was abundant. The basal clays contained a considerable quantity 

 of lignite. The following is a list of the fossils obtaiued between 

 the depths of 97 feet 3 inches and 136 feet:— 



Lignite. ' Pseudotrapezium (?) eaudatum 



Acrosalenia hemicidaroides Wright. (Lycett). 



■Serpula sp. j Pteroperna costatula (Desl.). 



Aft arte sp. ' Trigonia moretoni Lycett. 



Gervillia crassicosta Morris & Lycett. Trigonia pullits (!) J. de C. Sow. 



Modiola imbricata J. Sow. Trigonia of. scarbnrgensis'Ltyc&tt. 



Modiola sp. I Ncrincea sp. 



Nucula ('.). \ Nerinella funiculus (Desl.). 



Ostrea sp. | Nerinella sp. 



Pecten (Camptonectes) anntilaius (?) \ Pleurotomaria (?). 



<L de C. Sow. | Crustacean remains. 



Perm sp. [ Fisk-fragments. 

 Pholadomya sp. 



(iii) Great Oolite Series. [J. P.] 



Beneath the clays of the Forest Marble the cores showed a series 

 of marly limestones passing downwards (according to the borer's 

 record) through a thick band of dark grey sandy shales into marly 

 clays and limestones. The lowest bed is a thinly-bedded limestone 

 with lignite. Dr. Davies has described the microscopic structure 

 of a number of the limestones on p. 318, so that few further 

 observations need be added to his descriptions. Nearly all the 

 beds are dark grey, and this coloration is due to the presence of 

 numerous minute black fragments of limestone which are very 

 abundant in some of the clays. 



The uppermost bed of the section immediately underlying the 

 greenish clays of the Forest Marble is a compact, blotchy, grey 

 limestone ; and, although it differs somewhat in colour from the 

 ' Cream-Cheese ' top of the Great Oolite exposed in the Bicester 

 cuttings, it possesses so many of the characters of that bed that 

 its relationship was easily recognized. Dr. Davies's observations 



