August 31, 1882] 



NATURE 



429 



also at, or near Brading harbour, below St. Helen's. Remains 

 of Trionyx, or the fresh-water tortoise, large cerithia (C. vari- 

 abile), and Cyrena pulchra characterise these Ijeds 



The third group, or the Bembridge oyster beds, forma '■ 

 narrow but constant band between the marls and the limestones. 

 Marine conditions -ct in here, characterised by the abundance of 

 Ostrea vectensis, Nncula similis, Cytherca incrassala, Mytilus, 

 and Cerilhium. These beds Mere long mistaken for the "upper 

 marine" or Middle Headon strata. At Whitecliff Hay and 

 Brading harbour this grou.j may be advantageously studied. 



The fourth subdivision, or Bembridge limestone, includes 

 those beds exhibited at Binsted, Cowes, Calbouni, and Sconce 

 (but not the limestones of the I leadon series). It is important to 

 remember this when corrcliting the British Upper Eocene 

 deposits with those of the Continent. 



This remarkable limestone in Whitecliff Bay, forms a con- 

 spicuous feature in the clifls ; it is also the marked feature at 

 Bembridge ledge. When closely inspected it is found to be 

 c imposed of a number of distinct beds or strata. In ascending 

 order we readily recognise seven divisions, each characterised by 

 freshwater mollusca and some few land plants. 



Bed No. I. Concretionary limestone containing the fresh- 

 water plant Chara tuberculata, with Lymntia 

 longiscata. 

 „ 2. Greenish marly clay, Lym. longiscata and 



Planar bis. 

 ,, 3. Compact creamy yellow limestone, Lym. longis- 

 cata and L'lanorbis otigyratus. 

 ,, 4. Pale marly limestone, compact in places, full of 

 Paludina globulotdes, Lym. longiscata, //yd- 

 robia, and Cyclostoma mumia. 

 ,, 5. Greeni h white limestone, concretionary and 



fossilifcrous, containing Lym. longiscata, 

 /'Innorbis discus. /'. rotundaltis, P. Sowcrbyii, 

 P. obtusus. Helix occlusa, /Mix labryrintliica. 

 ,, 6. Crumbly white marl, with glo mlar concretion-, 



Chara tuberculata, Planorbis obtusus. 

 ,, 7. A similar bed to 6, with Planorbis discus. The 

 whole about 25 feet thick. 

 The strata along the coast and section are in many places 

 beautifully shown, and present peculiarities not elsewhere seen 

 in the island. 



The differe pcc between the upper and lower portions of them 

 is considerable, and may be separated — 



1. The Upper, Forbes termed the St. Helen's Sands. 



2. The Lower, the Ncttlesome Grits. 



The St. Helen's Beds, or Osborne and St. Helen's. 



Thee lie between the Upper //ctdon scries proper, containing 

 Potamomya and the Bembndge limestones. Thee beds are of 

 freshwater and brackish-water origin. 



Paludina (P. lento), Melanin: (M. costata, M. excavata), 

 A/elanopsis brevis and M. carinata. Chara Lytllii is the 

 Gyrogonite >S this limestone band, which on the east side 

 divides the Upper or Nettlestonc beds from the Lower or 

 St. Helen's sand-. 



Between the Bembridge limestone and the bracki h-water beds 



with Potatoomya-, that terminatethe Headon beds, a great series 



of stra a intervenes, which oil account of their min 1 dogical and 



logical peculiarities, deserve and hold an intermediate 



position between the middle and up|>er Eocene strata. 



Osborne Series in Whiteclifi p., 



Thickness 100 feet.— Hark red clays and bright rerl and 

 variegated clays occur, (l/clix occlusa, Planorbis discus, and 

 Lym nun longiscata.) 



Osdor.se Series between St. Helen's and Kvde. 

 Between Bradinj Harbour and Ryde secti >ns occur, and on 

 shore are se-n the rocky ledges below Seafield, and from St. 

 Helen', to Nettlestone. At WatchhouK Point, below St. 

 Helen's, the Bembridge limestone forms an extensive arch. 



Heauon Series. 170 feet thick. 



/lest se,n a: /leadon /Ml, Colwell Bay, and at Whitecliff Bay, 

 and their 1 <west divisions at Hordwell. Everywhere L'lanorbis 

 ttiomphalus characterises the fresh-water bands. 



Potamomya plana, and Ceii'hinm pseudocinctum abound in the 

 brackish-water beds Cytherca (Venus) incrassala, accompanied 

 by many shells, occur in the marine division. 



The group may be divided into three sections, Upper, Middle, 

 and Lower Headon. 



L'pper L/cadous.— These constitute the greater portion of ihe 

 Upper freshwater series. The mass of freshwater limestone 111 

 Headon Bill belongs to this section. Brackish in the upper pan, 

 abounding in Potamomya and Cyrena obovata, at Cliff End they 

 contain a cyrena (like C. pulchra). Cerilhium trr.onatum occur's 

 here abundantly, and Bulimus politus and Mclania muricata 

 abound. 



Middle //eadons. " The Headon inter marine or Upper marine 

 formation." — At Headon Hill these deposits were deposited 

 under brackish-water conditions, for, although Ostrea, Cythirca 

 incrassala, A'uculu di/ioidea, Natica deprcssa , /jucciuum labiatum, 

 and other sea shells are common, the upper and lower beds 

 abound in Cerilhium ventricosum, Cerilhium concavum, Ceri- 

 lhium pseudocitucum, Aeiilina concava, Nematura, cVr. which 

 are bracki-h or estuarine. A short distance further north, in 

 Colwell Bay, the upper and lower beds contain brackish-water 

 shells ; but the central part assumes a distinctly marine charactet . 

 Ostrea velala, S. Wood, is a characteristic species with numerous 

 marine genera, many of which are of Barton types. This central 

 part is known as the " Venus bed," from the presence of Cytherca 

 incrassala. The marine character of the Middle /leadon beds is 

 still more strongly marked at Whitecliff Bay (22 genera). The 

 lower portion of this series at Whitecliff Bay contains many 

 Brockcnhuist species, but at Colwell Bay we have no evidence 

 of ' charactei islic species from this horizon, or in the western side of 

 the island. 



Loioer Headons, fre-h and brackish-water series. 

 The e beds are 70 feet thick in Totland Bay, and 40 feet thick 

 in Whitecliff Bay. 



They consist of fresh and brackish-water beds abounding in 

 fossils resembling those of the upper division. Unio Solandri 

 and Cyrena cycladiformis occur here and are characteristic. 



At Headon Hill the thick bed of limestone in the Upper 

 Headon \- conspicu ,us in the cliffs, but it thins out rapidly 

 towards the north and disappears in an easterly direction. 1 be 

 Lower Headon contains a much less thick limestone at Headon 

 Hill, and it is represented by the band forming How Ledge 

 between Colwell and Totland Bays. 120 species have been 

 obtained from the I lead .n series; 104 mollusca, 9 Crustacea, 

 4 annelids, and three plants, land, freshwater ; and marine the 

 fossils of the Headon fluvio-marine series, are ;; gasteropoda; 

 ii pelycipoda ; polycipea I, balanus 1, Crustacea ':„ planta- \, 

 fish \. 



Professor Judd, in a paper communicated to the Geological 

 Society in May, 1880, on the Olizocene strata of the Hampshire 

 basin, having reference to the beds at Headon Hill and Colwell 

 Bay, m the Isle of U ight, endeavoured to show that the Colwell 

 Bay marine beds arc n it, as has been hitherto supposed, the 

 equivalents of the eof lid in Hill and Hordwell Cliff, but that 

 they occupy a distinct and much higher horizon in the Eocene 

 series. Assuming this to be the ease, a new classification and 

 nomenclature for the Upper Eocene series of Britain was proposed 

 by the author (Quarterly Journal of the Geological Society, vol. 

 xxxvi. 1880.) 



Professor Judd traced the history of previous opinion upon the 

 succc sion of the Tertiary strata down to the time of Professor 

 Edward Forbes and the Geological Survey, with the subsequent 

 labours of Mr. Bristow. Edward Forbe confirmed the previous 

 determinations r.f Professor Prestwicfa in his el borate researches 

 in the Isle of Wight Tertiarics. Forbes's life, however, was not 

 spared to enable him to complete his researches in this division 

 of the British strata ; his attention was chiefly confined to the 

 four uppermost Eocene members, or the Hempstead, Bembridge, 

 , and St. Helen's, ainl the 1 leadon beds. These 

 divisions were accepted and worked upon as a basis by the 

 Geological Survey. With rcgnrrl to ihese strata, Forbes main- 

 tained, as almost all previous observers hid done, that the beds 

 at Colwell and Totland bays are on the same horizon as those at 

 the base of Headon Hill and at Hordwell Cliff. 



Professor Judd'* view bas been questioned and refuted by 

 Tawney and Keeping, in an elaborate paper also read 

 before the Geological Society in May, 1881, (Quarterly journal 

 of ihe Geological Society, vol. xxxvii. 1881.) and in a subsequent 

 communication to the Cambridge Philosophical Society in the 

 same year, "On the Beds at Headjn Hill and Colwell Bay in 

 the Me of Wight." 



Tbe importance of a correct reading and classification of these 

 Middle Eocene strata in the lie of Wight, ai d their correlation 



