856 
~ 4 ‘ dey 
STRATIGRAPHICAL GEOLOGY. [Boox VI. 
reminding us of that of the lakes in Southern Africa.t The mam- 
malia increase in variety of forms. According to Gaudry the follow- 
ing chronological sequences of appearances and disappearances 
during the Oligocene period have been noted : * | 
ry 
gS oO 4 UGS 
Aon es 
4 oo . ° ‘ : 
ay B18 | Appearance of the genera Rhinoceros (?), Tapir, Palzocherus, 
SIRES shrew, Plestiosorex, Mysarachne, mole, musk-rat, Lutrictis, 
as oso Palxonycteris, Tetracus. Disappearance of Palxotherium, 
~ a es a A, Anoplotherium. Reign of Hyopotamus and Anthracothertum. 
5 gm & 
Dia Soe 
Ba od 
——Q 
— ( Appearance of the genera Cadurcotherium, Hyrachius, Entelodon, 
Zoos Anthracotherium, Dacrytherium, Chalicotherium, Tragulohyus, 
= i. Lophiomeryx, Hycemoschus (?), Gelocus, Dremotherium, Ther- 
sae | eutherium, dog (?), civet, martin, Plesictis, Plesiogale, 
OR Alurogale, Rhinolophus, Necrolenur. 
woe ( b) Pp 
Gey on 
ogag f | 
SES 0 
%SS4> | Appearance of the genera opossum, Ohevropotamus, Tapirulus, 
= Std one Anoplotherium, Hurytherium, COainotherium, Anchilophus, 
oe, a Acotherulum, Cebocherus, Xiphodon, Amphimeryx, Plesiare- 
Og mor & tomys, dormouse (?), Trechomys, Galethylaw (?), Hyznodon, 
Mee ag Adapis. Reign of pachyderms. The carnivora have still 
a cs BS partly marsupial characters. 
o.4"" 3 
oS 3 w 9 
Se em 
§ 2. Local Development. 
Britain.—Oligocene strata are but sparingly developed in this 
country. They occur in the Hampshire basin and Isle of Wight, rest- 
ing conformably upon the top of the Kocene deposits, and consisting of 
sands, 
clays, marls, and limestones, in thin-bedded alternations. These 
strata were accumulated partly in the sea, partly in brackish, and partly 
in fresh water. They were hence named by Edward Forbes “ the fluvio- 
marine series,’ and were subdivided by him as under, in descending 
order : 3 
Hempstead Beds.—Corbula beds (marine). Brown and greenish 
nodular clays and shelly beds (Corbula vectensis, C. pisum, Cyrena 
semistriata, Cerithium plicatum, Cyprids, &e.) . : , 
Upper fresh-water and estuary marls.—(Cerithium plicatum, 
Corbula vectensis, Cerithium elegans, Cyrena semistriata, Euchilus 
(Rissoa) Chastelli, Melania Nystii (inflata), Unio Austeni, &ec.) . 40ft. 
Middle fresh-water and estuary marls.—(Cyrena semistriata, 
Paludina lenta, Cerithium Sedqwickti, Melania fasciata, Panopexa 
Oft. Gin. 
minor, P. Gibbsii, &¢.) ; : ; ; ; Bort. 
Lower fresh-water and estuary marls.—(Melania muricata, Me- 
lanopsis carinata, Huchilus (Risso) Chastelli, Paludina lenta, with 
Chara, Gyrogonites, and other aquatic and terrestrial plants) . G6dft. 

' A, Milne Edwards, Oiseaua Fossiles. Boyd Dawkins, Karly Man in Britain, p. 54, 
2 Les Encnainements du Monde Animal, 1878, p. 4. 
* In the work already cited, p, 843. They were classed as Upper Eocene. 
