
~ 
Part IV. Sxcr. ii. § 2.] OLIGOCENE. 857 
Bembridge Beds.—Bembridge marls (Potamaclis (Melania) turritis- 
sima, Cerithium mutabile, Cyrena pulchra, Ostrea vectensis) . . 62K. 
Limestone (Limnza longiscata, Hyalinia (Helix) @ Urbani, Helix 
occlusa, Planorbis obtusus, P. oligyratus, Cyclotus cinctus, Amphi- 
dromus (Bulimus) ellipticus) : : : nye 15 to 25ft. 
Osborne or St. Helen’s Beds.—Clays, marls, sands, and limestones 
(Chara Lyelli, Cyrena obovata, Melanopsis carinata, and numerous 
species of Planorbis, Paludina, &e.) . : : ’ é ‘ 
Headon Beds.—Upper, consisting of clays and thick beds of lime- 
stone, with abundance and variety of fossils (Potamomya, Cyrena 
obovata, Nystia (Bulimus) polita, Melania muricata, Paludina lenta, 
Limnza longiscata). Middle, containing brackish- water and marine 
fossils (Ostrea flabellula, O. callifera, Cytherea (Venus) incrassata, 
C. suborbicularis, Pleurotoma odontella, Murex sexdentatus, Voluta 
spinosa, Pisania labiata, Ancillaria buccinoides, Cancellaria muri- 
cata, Cerithium concavum, &e. Lower, composed of fresh and 
brackish water beds with Cyrena cycladiformis, Unio Solandri, 
Helix, several species, &e. Among the more conspicuous fossils of 
the fresh-water part of the Headon beds are Planorbis ewomphalus, 
P. rotundatus, P. lens, and other species, Limnzxa longiscata, and 
other species, Paludina lenta; in the brackish-water beds Pota- 
momya plana, and Potamides cinctus; and in the marine bands 
Cytherea incrassata . ; : ; . : ; 133 to 175 ft. 
70 ft. 
Considerable interest attaches to the marine band forming the middle 
division of the Headon beds, as it serves for a basis of correlation between 
the English strata and their equivalents on the Continent. The band is 
well seen in the Isle of Wight, and occurs also at Brockenhurst and other 
places in the New Forest. It has yielded up to the present time 235 
species of fossils, almost all marine molluscs, but including also 14 species 
of corals, Of these organisms a considerable proportion is common to 
- the Lower Oligocene of France, Belgium, and Germany, and 22 species 
are found in the Upper Bagshot beds. 
The Oligocene or fluvio-marine series of the Hampshire basin has 
yielded a few vertebrate remains. Among these are those of rays 
(Myliobatis), snakes (Palzryx), crocodiles, alligators, turtles (Emys, 
Trionyx, numerous species), and a cetacean (Baleenoptera), while from the 
Bembridge beds have come the bones of a number of the characteristic 
mammals (Anoplotherium, two species, Palsotherium, six or more species, 
Cheeropotamus, Dichobune, Dichodon, Hyopotamus, two species, Lophiodon, 
Microcherus, Hyracotherium). The top of the fluvio-marine series in the 
Isle of Wight has been removed in denudation, so that the records of the 
rest of the Oligocene period have there entirely disappeared. 
It has been hitherto customary to consider as Miocene certain plant- 
bearing strata, of which a small detached basin occurs at Bovey Tracey, 
Devonshire, but which are mainly distributed in the great volcanic 
plateaux of Antrim and the west of Scotland. These strata have been 
regarded as equivalents of what are now termed Oligocene beds on the 
Continent. At the Bovey Tracey locality, which is not more than 80 
miles from the Eocene leaf-beds of Bournemouth and the Isle of Wight, a 
small but interesting group of sand, clay, and lignite beds, from 200 to 
300 feet thick, lies between the granite of Dartmoor and the Greensand 
hills, in what was evidently the hollow of a lake. From these beds Heer 
of Zurich, who has thrown so much light on the Tertiary floras of both 
1 A, von Koenen, Q. J. Geol. Soc. xx. (1864), 97. Duncan, Op. cit. xxvi. (1870), 
p. 66. J. W. Judd, Op. cit. xxxvi. (1880), p. 137. H. Keeping and E. B. Tawny, 
Op. cit. xxxvii. (1881), p. 85. 
