52 



HARDWICKE'S SCIENCE-GOSSIP. 



THE FOSSIL PECTENS OF THE UPPER 

 GREENSAND AND CHLORITIC MARL 

 OF TPIE ISLE OF WIGHT. 



By C. Parkinson, F.G.S. 



SOME of the drawings accompanying this paper 

 are from specimens found by me, most of which 

 are now included in the collections of the Geological 

 Department of the Natural History Museum, South 

 Kensington. During the last few years I have spent 

 a great deal of time and trouble in cataloguing the 

 fossil of upper greensand, chloritic (or glaucanitic) 

 marl, and chalk marl, at the south side of the Isle of 

 Wight, taking pains, at the same time, to separate the 

 fossils of each zone ; as a result of this care in 

 referring every fossil to its own horizon, we find 



near to Ventnor railway station ; the result corre- 

 sponds altogether with my previous measurement in 

 the same spot. At the same time it is only fair to 

 state that in different parts of the undercliff the 

 chloritic marl varies in thickness, as it apparently 

 fills up depressions in the stratum below. I am 

 certain, however, that six feet is an average thick- 

 ness, and that it may be divided into two divisions ; 

 35 feet fossiliferous, with base of hard phosphatic 

 nodules and crushed Pecten asper ; 2| compact, 

 darker grains, and few fossils. 



Mr. Etheridge thought that Pccfen asper was more 

 properly an upper greensand form, and very unusual 

 in the chloritic marl. In the five years' experience 

 I have had in the Isle of Wight, I have never been 

 able to find a single specimen of Pcctcn asper below 

 the phosphatic nodules referred to above. In that 



Fig- 31- — Ptxtoi asper. 



Fig. 30. — Pecten interstriatus. 



evidence of no less than three successive faunae 

 between the chloritic marl and the base of the upper 

 greensand. In a paper communicated to the 

 Geological Society in March, iSSi, I gave the 

 measurements of these rocks as found at St. Lawrence 

 and Ventnor, I. W., at the same time pointing out 

 how remarkably certain zones might be distinguished 

 and determined by the careful observation of the 

 paloeontological remains. In the short discussion 

 which followed, some astonishment was expressed 

 at my measurement of the chloritic marl, and at the 

 position I had given Pecten asper, while an opinion 

 was also expressed that such widely distributed 

 genera as Pecten and Lima were not of themselves 

 sufficient to form a guide in separating the zones of 

 life in the greensands. 



Since that time I have had an opportunity of re- 

 measuring the chloritic marl in a section of a quarry 



band, a few inches only in thickness, many specimens 

 may be found, all more or less broken, a fact which 

 would seem to indicate some violent and sudden 

 action by which the nodules were formed and the 

 molluscs destroyed. Fig. 31 is a specimen I found in 

 situ in the nodule band ; the denticulated ribs are 

 here visible, being worn away from the larger 

 specimen. It is most certainly a characteristic 

 species (though possibly derived) of the chloritic 

 marl. 



Pecten Beaveri (Sow.) also occurs plentifully in the 

 marl ; the valves of specimens are different from 

 chloritic and chalk marl respectively. 



Pecten orbicularis (Sow.) is a species common to 

 several zones in the upper greensand and marls. 

 Below the chloritic marl there lies twenty-four feet 

 of alternate bands of greensand and hard blue chalk. 



P. interstriatus (Seym.) in the second band of 



