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mals as water. The Sahara desert although elevated during the Tertiary was another faunal barrier and northern Africa was zoologically a part of Europe. In the far northeast the Behring Straits were formed and after a complete community of arctic, boreal and north temperate faunas had been established, the Nearctic region or North America was completely isolated from the Palearctic or Europe and Asia. (See Fig. III.)

Stratigraphy.-Faunally the strata record is far less exact than in the preceding Tertiary periods owing to the wide spread removal of easily eroded materials. Yet definite stratigraphic succession occurs in many places and upon the whole the faunal succession as shown in column V of the Table, p. 36, is as fully and definitely known as in any previous division of the Tertiary. In the sands of St. Acheul, near Paris, Elephas antiquus occurs at 7 metres, Hippopotamus amphibius at or below 5 metres, Elephas primigenius never below 3 metres. The most exact stratigraphic records are those of the caves near Schaffhausen for example; here a general succession of types is positively ascertained.

1. Preglacial, Elephas meridionalis Period

The typical preglacial deposits are the Forest Beds of Norfolk. The weight of opinion and of fact is all upon the side of considering these beds as Pleistocene. DEPÉRET ('93, p. 538), is strongly of opinion that they are transitional between Pliocene and Pleistocene with prevailing affinities on the latter side. He places with them as of the same age St. Prest (Eure et Loire), Durfort (Gard) where a magnificent skeleton of Elephas meridionalis was obtained for the Paris Museum; Malbattu, Peyrolles (Auvergne, Puy-de-Dôme).

From the list given by DAWKINS ('80, '94), SCHLOSSER and other writers the Preglacial period is found to contain:

12 Pliocene species;

32 Pleistocene species and races, now extinct;

17 Living species, of which 7 are Insectivora and I

Cheiroptera.

Some of the determinations are questionable.

Pohlig states

that the true Cervus megaceros hibernia is post-glacial, the preglacial type being more primitive; also that the straight tusked Elephas antiquus first appears in the north in the Mosbach interglacial bed; elsewhere he refers to it as occurring in the south of France (St. Prest) preglacial beds.

The remarkable feature of this fauna is the mixture of African and North Asiatic forms. The great Elephas meridionalis, a precursor of the Mammoth, is the most characteristic type.

The first traces of man in the palæolithic flints of the Cheléen type occur upon this level.

The climate, judging by the flora and Conchylien fauna, was somewhat cooler than that of the Upper Pliocene. The first arctic flora in England is in a layer which separates the Forest Bed from the glacial Boulder Clays.

2. Glacial and Interglacial, or Mid-Pleistocene

a. Lower Mid-Pleistocene. First Interglacial Period (Elephas trogontherii) Lower Stage, Pohlig.

In climate the early part of this period, immediately during and succeeding the first ice advance, was very extreme. None of the first ice advance fauna is known unless we except Elephas (primigenius) trogontherii or intermedius and Cervus elaphus, the latter being doubtfully recorded from the Boulder Clay of England. Here we find the first arctic and sub-arctic types in central Europe. Geologically, these post-glacial deposits consist (Rixdorf Beds) of gravels, conglomerates and sands, constituting (Pohlig) the highest post-glacial terraces, or Higher Terraces. It is marked by the first appearance of Elephas trogontheri, Rhinoceros merckii, R. tichorhinus, and the following species of northern type: Ovibos moschatus, Cervus (Megaceros) germaniæ. Among the new forms we note the megarhine rhinoceros, R. mercki, as most distinctive. The mammoth Elephas (primigenius) trogontherii succeeded the Elephas meridionalis of the preglacial beds.

b. Lower Mid-Pleistocene. First Interglacial Period (Elephas trogontheri) Middle Stage, Pohlig.

This stage marks the recurrence of a more temperate climate, first observed by Lyell and Evans in England and abundantly known in Germany and France. Two only of the characteristic Pliocene species recur, Hippopotamus amphibius, and Elephas antiquus. These alone have been universally cited as evidence of a south temperate climate but the more numerous northern types still living which are found in this stage constitute still stronger proofs of a north temperate climate.

Geologically the deposits are of fluviatile origin, consisting of river sands and gravels containing Hippopotamus, Rhinoceros merckii and Elephas trogontheri. Trogontherium cuvieri makes its last appearance here.

Geographically the southern continental depression has not begun and the Lower Pleistocene land bridges persisted. Parallel faunæ are those of Essex (Ilford, Grays Thurrock, Clacton) and Kent (Erith and Crayford) fully listed by Dawkins ('80, p. 397; '94, p. 243) and Woodward ('83). In Germany the typical fauna is that of Mosbach (Lepsius, '92, p. 652). The Mosbach and Essex faunæ give the following results : 4 Pliocene species, (including two living types);

7 Pleistocene species, now extinct;

16 Living species (including 2 Pliocene species). The characteristic Pleistocene species which are first recorded in Mosbach are Cervus megaceros, Cervus (Alces) latifrons, C. elaphus typus, C. Capreolus typus, Felis spelæa, Ursus spelæus, Bos taurus, Bison priscus; in Essex, Cervus (Megaceros) belgrandi, Hyæna spelaa. Among the living species recorded for the first time or making their first appearance at this stage are Rangifer tarandus, Sus scrofa, Equus caballus, Felis lynx, Meles taxus, Arctomys marmotta. The Essex Fauna is fuller but although of more southern latitude is not of more southern type, including the northern and north temperate forms Felis catus, Canis (Vulpes) alopex, Canis lupus, Ursus ferox, Ursus arctos,

Lutra lutra.

c. Mid-Pleistocene. Elephas antiquus stage, First Interglacial Period Upper Stage, Pohlig.

According to Pohlig the Mid-Pleistocene proper, or succeeding stage, was characterized by volcanic disturbances in central Europe and by the deposition of gypsum and tufas. Probably these earth movements were connected with the marked geographical changes brought about by wide-spread depression of the continental borders and isolation, which the same author assigns to this period. The fauna, typically represented in the Thuringian tufas, indicates a cooler or north temperate climate. Elephas antiquus is very abundant, making its last appearance north of Italy. The typical locality is the Thuringian Tufa in which Pohlig records 61 species. Parallel with this is the Taubach Weimar fauna.

In 1895, NEHRING ('95, p. 369) reported from this level what he regarded as the oldest human remains thus far found in Europe, consisting of two very large molar teeth resembling in some respects those of the chimpanzee; this he considered of Cheléen type. In the same year Newton described a human skeleton of Esquimaux type in the still older 'higher terraces' or Hippopotamus level; the antiquity of this skeleton is, however, rendered somewhat doubtful by the fact that the skull is of much newer type than those of Néanderthal and Spy, and the evidence for its extreme palæolithic age is not considered absolutely conclusive.

In this fauna Hippopotamus no longer appears—an indication perhaps of a decidedly colder climate. Elephas antiquus however persists and is most abundant. Among the other characteristic Pleistocene forms are Rhinoceros merckii which disappears soon after this stage; E. primigenius typus; Cervus gastaldi. The faunal list is provisionally analysed as follows:

3 Pliocene species still living (Castor, Hyana, Arvicola); 7 Pleistocene species, now extinct;

23 Living species (including living pleistocene Northern types).

The number of recorded living species increases, there being

a marked increase especially in the number of reindeer. The most important new living types are: the steppe antelope Saiga prisca (tartarica), the moose Alces machlis, the lemming, Myodes lemmus, the Siberian jerboa Alactaga saliens, Hystrix, Lepus timidus. These constitute a distinct invasion of north Asiatic forms into the southern steppes.

THEORY OF A MID OR SECOND GLACIAL ADVANCE

In all the preceding summary a certain faunal succession is noted consisting chiefly of elimination of southern types and introduction of northern.

WOLDRICH ('96) maintains that all the loess and cave types are of postglacial age-the tundre and steppe types alone representing the last great glacial advance-after which came the meadow or field (Weide-fauna) and the forest fauna (Waldfauna); he considers the alleged ice periods as mere local oscillations.

The possibility must also be freely admitted, as discussed by BULMAN ('93, p. 261), of the existence of south temperate types remote from the Ice Sheet; we find, for example, in southern Alaska, a very mild climate in proximity to great glaciers; similar conditions may have existed in southwestern Ireland and southern Europe.

Other authors such as Boule, have maintained the glacial age of the Tundre and Steppe fauna and the post-glacial age of the Forest fauna. If they are correct the theory of an interglacial or second glacial advance would lose its strongest support. It is evident, however, that such a succession of faunas might recur more than once. Nehring has observed in different localities (Westeregeln, Thiede), the unquestionable interglacial age of the steppe fauna and he considers Schweizerbild as interglacial.

d. Upper Mid-Pleistocene. Elephas primigenius Stage, Pohlig As we enter the next succeeding life stage, namely, the Loess and Cave Fauna of Central Europe, the stage of Elephas primigenius, Rhinoceros antiquitatis or tichorhinus and Rangifer tarandus we note the decline of Rhinoceros merckii and the ab

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