250 



Dr. PiTTON on the Strata below the Chalk. 



Ft. In. 



Ft. In. 



4. Slaty limestone in firm beds, alternating with blue fissile clay : 



a. Rough and irregular above 6 in. to 1 



b. Stone; firm and durable, abounding in Cyclades; — within the valves of-i 

 which are deposited beautiful casts of a small species of Cypris. See >l 

 Pl.XXI. fig. 76 1 



5. Alternations of very blue fissile clay, with thick slaty stone, containing Ostrea\ 



distorta J 



6. Stone ; continued downwards visible 



These lower beds are of different tints of blue and gray ; the gray by exposure becoming white, 

 and the blue portions graduating into a hard, somewhat splintery stone, which in some spe- 

 cimens might be taken for limestone of the carboniferous series ; some of the slaty strata alter- 

 nating with clay (3 above), consist of worn, rounded, fragments of shell and of stone, and are 

 very like some of the upper beds of Bermuda. The outer surface of the more uniform lime- 

 stones is here much eroded by the weather ; and when the masses are split, the natural partings 

 are frequently found to be furrowed or eroded with tortuous irregular channels, from half 

 an inch downward in diameter. 



Tlie pits along the south bank of the river, where the Purbeck series emerges from beneath 

 the heights of sand, afl"ord several good sections; — very much alike, and fairly represented by the 

 following detail of one at Dashlet. (See the Map, PI. VII. fig. 3.) 



Section of the Stone-pits at Dashlet. 

 1. Brown, loam-like clay, including, or passing into 2 



1 3 



2. Concretional, but nearly continuous masses of soft stone, with layers of Cy-"1 

 clades and Cypris, and oolitic particles about J 



The oolitic particles, when decomposed, leave empty cavities in the firmer 

 cement, which might be mistaken for casts of Cypris. 



3. Fissile stone, in irregular beds, almost entirely composed of Cyclades and") 

 Cypris J 



4. A group of clay and limestone : 



a. Thin slaty, calciferous clay, including b 



b. Delicately fibrous carbonate of lime, with impressions of Cyclas media "1 „ 

 on the surfaces adjoining the clay ; the beaks unusually sharp J 



c. Clay 



d. Flattened roundish masses of uniform white and gray stone, imbedded 1 „ 

 in the clay of c. and d. ; vertical cracks within, as in Septaria J 



e. Brownish clay 1 in. to 



f. Fibrous carbonate of lime 



g. Fissile clay, calciferous below 1 in. to 



5. Compact limestone, in some places bluish, containing very large Cyclades -i 

 (C major) ; a large flat bivalve (Unio?); small bones and palates of fishes ; [• 

 and fragments of Oslrea distorta, PI. XXII. fig. 2 J 



The slaty limestone in the pits hereabouts affords the same beautiful casts of Cypris as are 

 found at Dallard's, frequently inclosed within the valves of Cyclades, of which, in fact, the beds 

 are almost entirely composed. In other cases the surfaces of the strata are covered with im- 

 pressions of a small Modiola. The clay is often divisible into fragments, which are polished, 

 as if by friction under strong pressure. 



1 



1 3 



A 



h to 





1 6 



2 





1 





6 J 







1 4 





to 





• 1 C 



