Vol. 57.] 



OF ST. lYES AND ELSWORTH. 



81 



obtained from the workmen the following specimens dug out of the 

 Oxford Clay : — 



Eryma (?). 



Ammonites {Cardioceras) cordatus, 



Sow. (abundant). 

 A. (C.) excavatus, Sow. 

 A. (C.) Maries, d'Orb. 

 A. (Oppelia) oculatU8 (?) Phill. 

 A. {Aspidoceras) perarmatus, Sow. 

 Belemnites hastatus, Montf. 



Belemnites Oweni, Pratt. 

 Avicula iiKsquivalvis (?) Sow. 

 G-ryphcea dilatata, Sow. (abundant). 

 Nuculana sp. 



Protocardium striatulum (?) Sow. 

 Bhynchonella varians, Schloth. 

 Pseudodiadema versiporuTn, Woodw. 



It seems, then, that the yellow oolitic limestone here separates- 

 the Ampthill from the Oxford Clay. The outcrop of the E,ock is 

 very narrow here, owing to its dip and the slope of the ground. 



Some 200 or 300 yards north-east of the brickpit last described 

 the rising ground is certainly capped by an outcrop of yellow 

 ferruginous limestone ; the yellowish-brown soil contains many 

 fragments of it, and its outcrop must be much broader than in the 

 brickpit. Less than 200 yards north of Cot tenham Doles Yard 

 yellowish-brown marl, with yellow ferruginous and slightly oolitic 

 limestone, is seen in ditches. Many fragments of the Rock occur on 

 the top and on the northern slope of the high ground, as far as 

 LindselTs Parm, ^ mile farther east. South and south-east of 

 the farm abundant evidence of the rock is afforded by a trench 

 along the eastern side of the railway, where yellow marl full of 

 yellow and grey ferruginous oolitic limestone can be traced for 

 some distance. I found here Pleurotomaria sp., Exogyra nana, and 

 Serpula. Again in Heath Drain, where it is crossed by the 

 railway, an exposure of the St. Ives Rock is seen, apparently dipping^ 

 northward under Ampthill Clay. The Rock is, in part, a grey, 

 strongly oolitic limestone, with ironshot grains and weathering 

 yellow ; in part also, a creamy-buff limestone, with few ironshot 

 grains. I have seen a similar variation in the southern district ; it 

 seems to have been noted by Prof. Seeley at Elsworth. Fossils 

 were abundant here, and I identified the following : — 



Ammonites (Perisphinctes) plicatilis, 

 Sow. (abundant). 



Belemnites sp. (cast of phragmacone). 



Pleurotomaria sp. (probably PI. reti- 

 culata, Sow.). 



Bentalium sp. 



Pleuromya recur va (?J Phill. 

 Exogyra nana, Sow. 

 Gryphcea dilatata. Sow. (abundant). 

 Ostrea (Alectryonia) gregaria. Sow. 

 Collyrites hicordata, Leske. 

 Serpula sp. 



The strike of the rock hereabouts bends abruptly southward, and 

 the outcrop is unusually broad. Definite exposures require a width 

 of at least 400 yards, and other indications suggest a still greater 

 breadth. For some distance south of the road to Ely /SgrpitZa-coated 

 oysters and fragments of the Rock are found at the surface. IS'ear 

 a pump 200 yards south of the road material dug from the drain 

 shows many pieces of the Rock, large and small, in yellow marl. 

 East of this drain high ground runs southward to Holywell,. 

 and on this high ground is a brownish-yellow marly soil strewn 



Q.J. G. S. No. 225. 3 



