8 ME. G. W. LAMPLrGH OX THE JUXCTIOX OF [vol. Ixxviii, 



Thickness in feet. 



4. blue) platy claj-, rather silty in texture, with green-mottled 



{cont.) markings here and there : small smooth brown-coated black 

 phosphatic nodules, widelj' spaced, but with linear tendeucj' : 

 rusty joints often coated with small selenite-crystals, giving 

 blocky fracture, due to shrinkage and weathering with decom- 

 position of original pj-rites. Streaky green and crimson |-inch 

 layer in places at the base, resting on the iron-grit floor. Fossils 

 rare, except ' Belemnites minimus' and crushed ' Inoceramus 

 concentricus ' ; but there are some traces of crushed ammonites 

 and other shells. [Dr. Kitchin & Mr. Pringle record an ammonite 

 of the auritus-group, supposed to be Soplites cafillus (J. de C. 

 Sowerb}'), and yaiitilus deslongchampsianus d'Orbigny, along 

 with a few other fossils ; see joosfea, pp. 51-52J 4 



3. Iron-grit floor, 1 to 2 inches thick, with minor undulations, 

 abraded on the knobs, and with a little coarse gritty sand pre- 

 served in some of the hollows, capping ochreous grit and iron- 

 stone-breccia with calcareous patches and ramifying veins and 

 tables of iron-grit : as fullj- described in the previous paper, 

 p. 238 2to2| 



2. ' Silty beds ' : loamy greensand, clay, etc. ; as described in the pre- 

 vious paper (Bed F), but diminished in thickness and without 

 the underlying lenticles of iron-grit, sandy pyritous claystone. 

 etc. (Bed G) seen in 1902 about 2 



1. ' Silver sands ' (see fonner paper), worked to a depth of 18 to 



20 feet Top only shown. 



All tlie other Shenley Hill sections have exhibited only the 

 dark platy lower clays, usually with a ' creep ' of amorphous 

 clay above them, and this is the first section that has reached 

 high enough to reveal the incoming of the Upper G-ault fossils, 

 ' Inoceramus sulcatus ' and the keeled ammonites, although these 

 forms have long been known to occur at another pit near Heath 

 House, 900 yards west of the Shenley Hill pits (see p. 28). 



The band of phosphatic nodules 5 a is of particular interest, both 

 from its structure and from its fossils. There can be little doubt 

 that it is a prolongation of the nodule-bed seen by Jukes-Browne 

 in 188-1, in a brickyard-section north of Leighton Buzzard, from 

 which he obtained numerous fossils, including eight species of 

 ammonites (see p. 27). described as a 'mixture of Lower and Upper 

 Gault species.' ^ The nodules are distributed rather sparsely and 

 irregularly in a layer which could be traced horizontally for 12 or 

 15 yards, m the top breakaway, before being hidden by the slip. 

 The layer was unbroken, but showed some minor undulations pro- 

 bably due to slipping, the pale marly clay above it being all more 

 or less affected by ' creep.' It does not contain any extraneous 

 coarse transported matter, differing in this respect entirely from 



^ ' The Cretaceous Rocks of Britain — vol. i : The Gault & Upper Greensand 

 of England' Mem. (ieol. Surv. 1900, p. 285. In our previous paper {op. cit. 

 p. 245) I presumed that the brickyard was that, now disused, on the 

 south-east side of the road from Leighton to Shenley Hill, 1100 yards 

 south of the sand-pits ; but I have since found that the place referred to was 

 a working, now obliterated, near the Heath House sandpit (postea, p. 28). 



The nodule-band in Harris's pit does not appear to have been exposed in 

 1919 when Dr. Kitchin & Mr. Pringle examined the section, as they state 

 (Geol. Mag. 1920, p. 61) that 'Xo nodule-bed similar to that described by 

 Jukes-Browne has been seen in any of the sections examined by ns, and we 

 are unable to test the value of his record.' 



