derived partly from White's Pit (fig. 4), and partly from Slade's Green, between the former and Crayford.

The comparative abundance of the species from each of these localities is also worthy of note. Bos primigenius is abundant in all; Elephas primigenius is most abundant at Ilford, Erith, and Crayford; while E. antiquus is comparatively rare. The latter species on the other hand is most frequently met with in the brick-pits of Grays Thurrock.

Before, however, I pass on to the range of the mammalia found in these deposits, there remains a most important point to be discussed. Were these animals found in different portions of the same section, the older forms in the lower, the newer in the upper parts? Such, indeed, was the hypothesis upon which Dr. Falconer strove to reconcile the association, at Brentford, of Pliocene species with animals clearly proved to have been of Postglacial age, in the journal of this Society; and such was the view he took of the mammalia found at Crayford. Knowing the value of the smallest of his hints, I have over and over again gone over the pit in company with Dr. Spurrell, and with Mr. Flaxman Spurrell, to find evidence for this view, and have come back each time more and more convinced that the mammalian beds, 4 & 5 of fig. 3, are of the same age, and that the animals found in those beds were living in the Thames Valley at the time of their deposit. The evidence, indeed, of the association of species at Crayford is corroborated by that of the sections at Ilford and Grays Thurrock. The proof of the tichorhine Rhinoceros being associated with the leptorhine and megarhine species, is to be found in the cabinets of Drs. Cotton and Spurrell, and of Mr. Grantham. For the proof that these three species have been rightly determined, I must refer to the monographs on their dentition in the Natural History Reviewt, and to that now in the hands of the Geological Society.

B. Range of the species. The above list of mammalia enables us to draw some important inferences about the deposits whence they were derived. The interest centres more particularly on the genera which composed Baron Cuvier's group of the Pachydermata, namely, Elephas and Rhinoceros. The Carnivora are such as might have been derived from any Pleistocene cave- or river-deposit in Britain; and, with one exception (the Cave-Bear), they still survive in some quarter of the world. Of the Ruminants, the great Urus probably survives in our larger breeds of domestic cattle, and the Aurochs or Bison still ranges through the temperate zones of North America, and lingers on in Europe in the Lithuanian forests, under the protection of the Russian government. Extinct in the high northern latitudes of Asia and America, it has left its bones, along with those of the Elk, Reindeer, Musk-sheep, and Mammoth, in the frozen loam that caps an ice cliff in Eschscholtz Bay §, to prove that it * Quart. Journ. Geol. Soc. vol. xiv. p. 83, 1857. + Vol. v. p. 399, 1865. See paper by the author in Quart. Journ. Geol. Soc. vol. xxii. P. 391, 1866. Zool. H.M.S. 'Herald;' and Beechey's 'Voyage to the Pacific,' Appendix by Dr. Buckland.

shared with those animals the northern shores of the American continent. Of the Cervidæ, the Irish Elk is alone extinct, and, having begun to live in Præglacial times in the Norfolk forest-bed, and having sufficient elasticity of constitution to survive the cold of the Glacial period, ranged through the Postglacial division of the Pleistocene, and at last died out in the Prehistoric period, not without giving room for the suspicion that the hand of man was one of the causes of its extinction. The Red Deer and the Roe Deer, its contemporaries with a parallel range, have lived on to the present time in Britain, protected by the law, but dwarfed in stature from their banishment to the wilder and more inhospitable regions by the inroads of civilization on their ancient haunts. The three species of Elephant, all of them utterly extinct, have a very unequal range in both space and time. The Mammoth, Elephas primigenius, occurs in the Præglacial forestbed of Norfolk, and, having been defended from the intense cold of the Glacial period by his clothing of hair and fur, is most abundant in the Postglacial deposits of France, Germany, and Britain, and in the frozen gravels of Russia in Europe and Asia, and of Eschscholtz Bay on the shores of North America. Its remains are found in the EuropeoAsiatic continent north of a line passing through the Pyrenees, the Alps, the northern shores of the Caspian, Lake Baikal, Kamtschatka, and the Stanovoi Mountains. The discovery of the frozen carcase by a Tungusian hunter in Siberia in 1790, and the representation of it, graven by the Reindeer-folk in the caves of the Dordogne' on a fragment of fossil ivory, prove that it was well defended against the cold; and its association with the Lemmings at Salisbury, with the Musk-sheep at Freshford† near Bath, and with the Reindeer universally in the Postglacial deposits, proves that it was fitted for enduring a very low temperature. The Elephas antiquus‡, found abundantly in the forest-bed of the Norfolk shore, and in some few deposits of unequivocally Postglacial age (as those of Lexden, Oxford, and Bedford), occurs in the Pliocene strata of France and Italy, and in the caverns on the shores of the Mediterranean, at Malaga, Gibraltar, Sicily, and Malta. It is, indeed, as remarkable for its southern as the former species is for its northern range. It appears to me to be a Pliocene species that lived in great numbers in Britain while the Præglacial deposit on the Norfolk shore was being formed, that was gradually supplanted by the Mammoth and driven southward by the lowering of the temperature. It occupied in Pleistocene times precisely the same climatal relation to the Mammoth as the Waipiti does now to the Reindeer in North America, the former being adapted for a mild or even hot climate, the latter being fitted to endure all the severity of an Arctic winter. As the climate gradually became colder, the former species would replace the latter in any given district; as the climate became warmer it would yield to the latter. To some such oscillation of temperature I would * Revue Archéologique, 1866.

↑ All the Mammalia cited from British localities have been examined by the author, and, for the most part, have not yet been put on record.

See Dr. Falconer's papers, Quart. Journ. Geol. Soc. vol. xiii. p. 307, 1857; vol. xxi. p. 253, 1865.

attribute the occurrence of the remains of these two species in the same deposits. The headquarters of the Elephas antiquus, into which the Mammoth never penetrated, was in Pleistocene times Southern Europe, bounded to the north by the Alps and the Pyrenees-just as that of the Mammoth, in which Elephas antiquus has never been discovered, is North Germany and the large wooded plains of Northern Russia. The debateable district, over which each of these species ranged according to the season, would, on this hypothesis, be the districts between these two areas, England and Central Europe, where their remains have been found commingled: the fact that the varying temperature in northern regions now regulates the migration of the herbivores, and causes a continual oscillation of animals to and fro over a given area, lends great weight to these views. The third species of Elephant, E. priscus, has only been determined by the late Dr. Falconer in three British localities-Grays Thurrock in Essex, an uncertain locality in the Thames valley, and in the forest-bed of the coast between Cromer and Lowestoft. It occurs also in Italy (in the Pliocene strata of the Romagna) and possibly in Central France. The Horse varies considerably in size; and to those who think themselves justified in ascribing the larger remains to the true Horse, and the smaller to the Zebra, Quagga, or Ass, there may seem reason for believing that two species or varieties of Equus were living at the time the Lower Brick-earths of the Thames valley were being deposited+. The examination, however, of a very large series of Equine remains from all parts of England, and from Pleistocene deposits in France and Germany, leads me to the conclusion that, in the days before Man's influence in modifying the animals in contact with him was felt, there was considerable variation in the size of the Horse, dependent probably upon various conditions of life, food, habitat, and climate; and as these varieties constitute an unbroken series from animals of the largest to those of the smallest size, there being no difference of form, I see no reason for M. Puel's and Professor Owen's insertion of the Ass into the list of the Pleistocene mammalia. The range of the Equus fossilis was coextensive with that of the Mammoth in the Pleistocene period; it is unknown in the Pliocene strata of France, Germany, and Italy; and its first appearance is in the Præglacial forestbed of Norfolk. It cannot be differentiated specifically from the common Horse.

We have already seen the unequal ranges of the three species of fossil Elephant; the species of Rhinoceros found in the deposits under consideration afford an exact parallel. The stout-limbed massive tichorhine Rhinoceros, possessed of two horns, and with foldless skin, ranged throughout Pleistocene Europe and Asia, north of a line passing through the Alps, Pyrenees, the head of the Caspian, and Lake Baikal. This species did not cross, along with the

* See "Introduction to British Pleistocene Mammalia," Palæont. Soc. vol. for 1864, 46 et seq. p.

+ See Owen, article "Equus," Foss. Mamm. 8vo, 1846.

Bull. Soc. Géol. Fr. 2me série, tom. ix. p. 244, 1854.

Mammoth, Behring's Straits into America; nor in time did it range so far back as the latter animal, being absent from the forest-bed, and having the Brick-earths at Ilford, Crayford, and Wickham as its earliest resting-places. It was a northern form, ranging up to the highest latitudes, and, unlike any of the living species, had its body defended from the cold by a thick clothing of wool. The second, or the leptorhine, species is that determined first of all by Professor Owen from Clacton, and is named from its supposed identity with the leptorhine species of Baron Cuvier from the Val d'Arno. As, however, the former is defined by Professor Owen as the "Rhinoceros à narines demi-cloisonnées," and the latter by Baron Cuvier as "R. à narines non cloisonnées", it is clear that these two species are not identical. In consequence of the conflict of evidence as to the existence of a bony nasal partition in the Italian skulls upon the drawings of which Baron Cuvier's species was based, and because he has confounded together all the non-tichorhine species of Pleistocene Rhinoceros under the common name of leptorhine, I have preferred to retain the name of R.leptorhinus of Professor Owen, as having been used in Britain for a group of remains truly and accurately defined under that name in 1846, rather than adopt the name which the late Dr. Falconer applied to the same species, R. hemitachus, by turning Professor Owen's definition of Rhinoceros à narines demi-cloisonnées into a Greek specific name‡. The leptorhine species of Owen ranges, in space, throughout England and Auvergne, and in time from the Thames-valley deposits to the epoch of the caverns of Gower, Wookey Hole, Kirkdale, and of the deposit of Bielbecks in Yorkshire. Unless that of Clacton turns out to be Præglacial, which is not yet proved to be the case, it has not been found in any strata formed anterior to the great Glacial era. It was a slender-limbed animal, and, from its limited northern range, was probably not able to endure the same severity of climate as its tichorhine congener. The third species, or Rhinoceros megarhinus of De Christol §, which I was able to determine satisfactorily as occurring in Britain in 1865 ||, stands in the same relation to the tichorhine species as the Elephas priscus does to the Mammoth. Its headquarters are to be found in the Pliocene deposits of Italy, whence it ranges northwards across the Alps into the French Pliocene beds. I am indebted to the courtesy of the Rev. John Gunn for being able to determine its remains in the forest-bed of Cromer. In the Thames-valley deposits under consideration, it is comparatively abundant, especially so at Grays Thurrock. With the exception of the above localities, it is found nowhere else in Britain. I am inclined to view it as one of the links binding the Pleistocene period to the Pliocene. Like the leptorhine it was possessed of two horns and was of slender build. It is differentiated Op. cit. pp. 356-382.

† Oss. Foss. tom. ii. p. 110. 4to. 1825. See Nat. Hist. Rev. vol. v. (1865), pp. 400-1.

The R. leptorhinus of Dr. Falconer = the R. megarhinus of De Christol, and it is so used throughout his paper.

§ Ann. Sc. Nat. 2d series, Zool., tom. iv. p. 42-112, 1865.

Nat. Hist. Rev. vol. v. p. 403, 1865.

from the latter by the enormous development of the nasal bones and the absence of the cloison or long partition between the nostrils.

Of the Wild Boar there is nothing to be said, except that it ranges from the forest-bed of Norfolk up to the present day, and is probably the lineal ancestor of that still alive in the wilder parts of Europe. It was, however, comparatively rare in the Pleistocene period, occurring only in 4 out of 26 ossiferous caverns, and in 4 out of 35 stratified deposits, which constitute my Tables of distribution of British mammalia, which I hope shortly to publish in the works of the Palæontographical Society.

The Hippopotamus major is to be placed in precisely the same category as the Elephas antiquus--as a Pliocene species that passed northwards over the Alps into France, England, and Germany, into what must have been the area in which the Northern and Southern faunæ met. Its occurrence in association with the remains of northern animals may be explained in the same way as that of Elephas antiquus, and is probably due to oscillation of climate-a view that Sir Charles Lyell has adopted in his 6th edition of The Elements,' in 1865.

The last two species, the Beaver and the Water-Rat, present no points that are useful for my present purpose relative to the Brickearths in question.

y. Relation to Praglacial and Postglacial Faunas. Such is the brief epitome of the fossil species, and their range in space and time; let us now pass to the consideration of the value of their evidence in stamping the relative age of the deposits in which they occur, as compared with the Præglacial forest-bed, the Postglacial river-beds, and the ossiferous caverns which are probably of Postglacial age. The following Table is an abstract of the larger one bearing on this question, which was constructed after an examination during more than five years of British and Irish collections of mammalia.

A study of this Table enables us to draw important inferences as to the geological age of the Lower Brick-earths. Passing over all the species which are common to the 4 columns, and, therefore, of no classificatory value, the presence of Elephas priscus and Rhinoceros megarhinus indicates the affinity of the group to the Præglacial deposits of Norfolk and to the foreign Pliocene strata. The tichorhine and leptorhine Rhinoceroses, on the other hand, point towards deposits of clearly defined Postglacial age. It was probably this peculiar clash of evidence that led Dr. Falconer* to believe that the organic remains must represent two geological epochs, and especially because these animals had never before been found in association. For any other fact in corroboration of his hypothesis I have sought in vain. The beds under consideration are also as remarkable for the absence of some as for the presence of others of the Pleistocene mammals. The Præglacial Trogonthere, Rhinoceros Etruscus, Elephas meridionalis, Sorex moschatus and Cervus dicranios are absent on the one hand, the entire group of Postglacial Arctic mammalia, the Glutton, * Op. cit.