216 REV. J. r. BLAKE ON THE 



agree with those at Chicksgrove*. This upper Portland bed is 

 often separable into two, the upper being more broken, but having 

 abundant Trigonice at its base, which in most northern quarries 

 are much perforated by small Lithodomi. The lower block makes a 

 solid building-stone, which is often the object of the quarries. The 

 total thickness of this portion is pretty uniform at about 4 feet, 

 however much the minor more consolidated bands may vary. In the 

 quarry at Bierton, near Aylesbury f, the character seems different ; 

 for the fossils are Mytilus pallidus and some unrecognizable bivalves, 

 and the resulting rock is much softer. This latter character, how- 

 ever, is repeated at Coney Hill, near Over Winchenden, where is a 

 very important section ; examined, however, in the direction of the 

 dip, along the road from Aylesbury to Thame, it retains the cha- 

 racter at its escarpment, but is diminished to 3 feet. The ordinary 

 Trigonia is T. gihbosa ; but Ssemann mentions T. ? Pellati as from here 

 at Hartwell, and Dr. Fitton mentions the only Belemnite known 

 in the Portland Stone as coming from this at Quainton. 



Wo. 2 is a more or less creamy limestone, but not always retain- 

 ing that character, and having a very fossiliferous band at the base. 

 It is, indeed, divisible into three blocks, when the upper part is the 

 most creamy and abounds in small well-preserved fossils, especially 

 Natica ceres, the middle is a harder block, and the basal portion is 

 hardened by the great abundance of Trigonice and other shells. At 

 Coney Hill this part is thicker than usual, and the three blocks are 

 4 feet, 4 feet, and 1 foot respectively, the top one very rich in fossils. 

 The lower parts of this are of considerable economic value in the 

 northern portion of the area, where they are the object of the 

 quarries for building-stone and lime ; and a large part of the village 

 of Whitchurch has this for its natural paving. Where the base is 

 consolidated by shells, the thickness is from 8 to 9 feet on the 

 whole; but towards the south the lower part loses its abundant 

 shells, which become more uniformly distributed, and it becomes a 

 brown non- creamy limestone, called the " greys," with an underlying 

 whiter rock, making, with the upper creamy parts, a total thickness 

 of 13 feet. These features are seen in the quarries at Brill and 

 Crendon. From Dr. Pitton's account of a pit near Stukeley, it would 

 appear, on the other hand, to diminish towards the north. The 

 fauna of this portion is extensive. 



Fossils of the Creamy Limestones of BuckinghamsJiire. 



c. Ammonites boloniensis {De Lor.). I Natica elegans (Sow.). 



0. triplex (Soiv.). c. ceres (Be Lor.). 



pseudogigas (Bla/ce). \ incisa (Blake). 



Belemnites, sp. J ( Marcousana§). 



Alaria Beaugrandi (L>e Lor.). [ ( Hebertana §). 



* The Purbeck beds here also agree in having flinty masses in them. 



t The spot is marked by a fault on the Survey Map, and Gault and Green- 

 sand introduced, of which there is no sign in the quarry. 



J Fide Dr. Fitton. 



§ Fide M. Ssemann. I have seen none like them, though looking particularly 

 for them. 



