August 31, 1882] 



NA TURE 



43 x 



behind ihe top of the cliff, between the chines. This being the 

 only part where it is missing from the cliff is proof of its con- 

 tinuity from Watden Cliff to the north-east corner of lleadon 

 Hill. 



The authors describe in the most careful manner the Lower 

 Headon beds of the cliffs between Weston and Widdick Chines, 

 much of the space in which is hidden by grassy slopes, but the 

 connection cannot be doubted. 



The Lower Headon of Warden Cliff.— "The lowest beds of 

 this series are seen below the Totland Bay Hotel at Weston 

 Chine, and all are below the Venus bed. A remarkable feature 

 in the lowest portion are five thin Lymnaean limes'.ones, con- 

 taining chara seeds. These five limestones at low wa'er form 

 five submarine ledges parallel to thegreat ledge at Warden cliff" 

 (Warden ledge). Above the e five beds and the sands containing 

 Potamoma comes the concretionary calcareous >atid rock which 

 forms Warden Ledge. It crops out at the top of the cliff 

 below the flagstaff ot the coastguard station. Succeeding these 

 is the Unio bed {U. Solandri) and associated with Melanin 

 turritissima. The How Ledge limestone succeeds and forms 

 the summit of the Lower Headon series. This limestone is 

 denuded away in the centre of Totland Bay, where we have 

 evidence and may infer the summit of the anticlinal to be near 

 the old wooden pier. The thickness of the Lower Headon in 

 Warden cliff is 72 feet, and from that to 87 feet before reaching 

 the yellow sands of the Upper Bag-hot. 



The whole of ihe cliffs between We>t n and Widdick Chines 

 ara occupied solely and throughout by Lower Headon beds, and 

 the Colwell Bay marine bed extends all through Warden point 

 and cliff, where it rests upon, or is supported by the How Ledge 

 limestone. Between Warden Battery and Weston Chine the 

 Col well Bay marine bed (Middle Headon) is maintained in all its 

 integrity. 



Middle Headon of Colwell Bay. — "The Neritina bed at the 

 south-west end of the bay is well seen a little short of Colwell 

 Chine. Above this comes the ricl est part of the ' Venus bed' 

 — the fossil in which (Cytheria inciassata) strew the tumbled 

 clays and commingle with recent shells on the shore." Oitna 

 velala, as at Headon Hill, is abundant above the part richest in 

 Cytherea. This oyster occurs in vast abundance in the centre of 

 the bay between Colwell and Bramble Chine-, crowding out 

 other fossils and forming a massive oyster bank about 20 feet 

 thick. The Venus bed here is altered in character, and abun- 

 dantly occurring with Cytherea inctassata are Murex stxden* 

 /a/us, Pisauia labiata, .Yatica labella/a, Nerila aperta, Ceflthium 

 variabile, and Os/rea vela/a." 



Upper Headon of Colwell Bay. — The horizon of Cyrena 

 Wightii is a marked feature here, associated with Corbicula 

 obovata ; Cerithium trizonatum also occupies one horizon just 

 below the buff-c jloured Lymnise limestone forming a narrow 

 band with green clays : Serpula tenuis is equally characteristic, 

 occurring at the same horizon both here and at Headon Hill, 

 viz. in the Upper Potamomya clay just above the Lymnaea lime- 

 stone. 



Pal/Eontological Evidence 



Having noticed the stratigraphical succession of the several 

 divisions in the beds at Headon Hill and Colwell Bay, I now 

 proceed to draw atention to the distribution of the fossils. 



The authors of the paper have di.-cussed the questi n as to 

 whether the Colwell Bay has any more affinity with the Brucken- 

 hurst fauna than has the Headon Hill bed ; and they compare 

 the fauna both of the Colwell Bay and Headon Hill marine 

 beds. This they do by separating in tabular form the fauna of 

 all the localities which are to be compared together. The 

 splendid collection of Tertiary fossils belonging to the late Mr. 

 F. Edwards, and now in the British Museum, has formed the 

 basis of their comparison, while their own researches have added 

 occurences still more conclusive as to the correlation of species 

 in the areas under examination and consideration. The authors 

 obtained during their re-earch in the Isle of Wight many species 

 in the marine bed at Headon Hill which do not exist in the 

 Edwards collection from that locality. " 1 he test as to the 

 contemporaneity of the beds in question is not to be obtained 

 from the rarer forms only, but from a comparison of the 

 commoner and more characteristic species." No less than fifty- 

 eight species were obtained by the authors from the Middle 

 Headon of two localities, Colwell Bay and Headon Hill, nine- 

 teen of which appeared in and came up from the Barton beds, 

 and with seven exceptions all the fifty-eight forms came from 

 both horizons. 



It has been stated that the "strata at Colwdl Bay an of 

 purely marine origin, while the so-ca led Middle Marine beds of 

 Headon Hill and Hordwell Cliff are of totally different character." 

 Mes rs. Tawney and Keeping obtained from the marine series at 

 Colwell Bay the bracki-h-water genera Cerithium, Cyr.na, 

 Hydrobia, fymucea, Paludiua, Planoibis, Melania, a. d Me- 

 lauopsis, although said to he fcund only at Headon Hill. It has 

 also been stated that certain species of Cerithium are confined 

 to Headon Hill, and do not occur in Colwell Bay, and that 

 through this serious errors in our clajsification have been 

 detected, as well as in the correlation of the strata under 

 Consideration. 



'I he presence of Cerithium concavum in the Venus bed abun- 

 dantly at Colwell Bay, and we may add from private informa- 

 tion from Mr. Keeping that he has found it also at Whiteclift 

 Bay in ihe same positiori, removes all doubt as to the non-occur- 

 reuce of the z< ne in that locality. As has been stated, the 

 jpecies is not so common as at Headon Hill. 



There is but one marine bed, and that is known only in the 

 Middle Headon. The place of the Brockenhurst bed is at the 

 lowest hoiizon in the Middle Heador, but it does not appear at 

 Colwell Bay or anywhere in the west end of the island. 



Middle Headon of Whitecliff Bay. It has been stated that the 

 Colwell Bay bed is placed in the Brockenhurst, which is said to 

 occupy a higher horizon than the Headon Hill and Hordwell 

 marine bed. The true place of the Brockenhurst fauna in the 

 Isle of Wight is confined to one zone, and that at the base of the 

 the Middle Headon serie-, and only at Whitecliff Bay or in the 

 New Forest. 



The Geological Survey do not mention by name the Brocken- 

 hurst bed in their verticil section [Sheet 25] of Whitecliff Bay, 

 as its peculiar fauna had not been recognised at that time. It is 

 easily identified, how ever, in their section as the basement bed of 

 their Middle Headon, the whole of which is given as 90 feet 

 thick. 



Brockenhurst Zone at Whitecliff Bay. — At the time the Geo- 

 logic il Survey section was made, this bed at Brockenhurst was 

 unknown, and its fauna undescrihed. Subsequent observers 

 have recognised the Brockenhurst fauna in the lowest bed (2 

 feet thick) of the Middle Headon at Whitecliff Bay. Sixty-nine 

 species are known here, and 104 uccur at Brockenhurst. 



Affinities of the Brockenhurst Fauna. — If we take the whole 

 Brockenhurst faun;", including the eighteen corals (special to the 

 zone) we obtain a total of 151 species, of which from 74 to I I 

 pass up from Barton. 



Mes rs. Tawney and Keeping supply a list of 53 species from 

 the Brockenhur-t zone obtained from the Whitley Kidge Rail. 

 wayCuttiig, New Foiest. Fifty-one of these 53 forms have 

 occurred in the 2-foot bed at Whitecliff Bay, 27 of which pass 

 up from the Barton or Bracklesham beds. 



The palaconlological evide ce therefore accords with the 

 stratigraphical. 



Rdalion of Colwell Mat incto Brockenhurst Fauna. — Examina- 

 tion gives us 29 per cent, of Barton forms in the Colwell Bay 

 bed. In the Brockenhurst bed the ratio was al out 50 per cent., 

 and in the Headon marine bed, 29 per cent. Examination also 

 of the more characteristic Colwell and Headon marine fossils 

 shows that these faunas are practically identical— and also shows 

 that only certain Brockenhurst species occur at Colwell Bay, and 

 nit at Headon Hill. They are Scalaria tessellala and Tellina 

 affinis, this latter a Barton f roi, while those occurring at 

 Headon Hill, and not at Colwell Bay, are Marginella wstuarina 

 and Cardila paucicostata, only ''two in each case, which 

 amounts to perfect equality." If we take into account those 

 common to the Colwell and Headon marine beds, and not 

 occurring at Brockenhurst, we fi. d twenty- ix species. It is 

 therefore evident tint the Brockenhur-t fauna is not identical 

 with that of the Colwell Bay bed, and not newer than that of 

 Headon Hill. 



Thus fossil as well as stratigraphical evidence shows that the 

 Colwell Bay bed is identical with the Headon Middle Marine. 



The same twofold proof demonstrates that the Brockenhurst 

 bed, where present, lies at the base of the Middle Marine 

 Headon beds, end immediately above the Lower Headon. 

 This Brockenhurst bed is absent at Colwell Bay and Headon 

 Hill, but occurs at Whitecliff Bay, Brockenhurst, and Lynd- 

 hurst. 



The propo al by Prof. Judd to extend the name of the 

 Headon series so as to include all the beds between the Barton 

 and Brockenhurst series, and call them the " Headon Group," 



