348 



THE CIVIL ENGINEKR AND ARCHITECT'S JOURNAL. 



[Nov, 



there is no anatomical character hy which the present wild boar can be 

 ilistingiiishecl specifically from that which was conlcmporary will) the 

 mammoth. The reindeer has, relatively to Hrilain, been exterminaled, nor 

 will our present climate permit its existence here. With llie diminution 

 of the fireat herbivora, which ^vouid naturally follow the liiuilation of their 

 range when England became an island, that of the carnivora, dependent 

 on them for food, would inevitably follow. And not here only, but like- 

 wise on the };reat continent over which they ranf;ed, which would indicate 

 that the extirpatiPR cause, if it were extrinsic to their own constitution, 

 liad been due to changes of the earth's configuration and climate much 

 more extensive than could be connected with the insulation of so small a 

 jjortifin of Europe as Britain. 



Thus, continued tlie Professor, in the endeavour to trace the origin of 

 onr existing mammalia, I have been led, by long researches on the fossils of 

 this island, to view them as descendants of a fraction of a peculiar and 

 extensive mammalian fauna which overspread Europe and Asia at a period 

 geologically recent, yet incalculably remote and long anterior to any evi- 

 dence on record of the human race. It would appear, indeed, fi*om the 

 comparisons which the present state of palaionlology permits to be insti- 

 tuted between the recent and extinct mammalian faun* of otlier great 

 natural divisions of the dry land, that these tlivi&ions also severally pos- 

 sessed a stries of mammalia as distinct and peculiar in each during the 

 pliocene period as at the present day. 



Compurison with the Exlincl Animals nf other Countries. 



When such a comparison is restricted to the fauna of a limited locality, 

 especially an insular one like Great Britain, the discrepancy between the 

 pliocene extinct and the existing groups of mammalia appears to be ex- 

 treme. But if we regard Great Britain in connexion with the rest of 

 Europe, and if we extend our view of the geographical distribution of 

 extinct mammals beyond the limits of technical geography, — and it needs 

 but a glance at the map to detect the artificial character of the line which 

 divides Europe from Asia, — we shall then lind a close and interesting 

 correspondence between the extinct Europreo-Asiatic mammalian fauna of 

 the pliocene period and that of the present day. The very fact of the 

 pliocene fossil mammalia of England being almost as rich in generic and 

 specific forms as those of Europe leads, as already staled, to the inference 

 that the intersecting branch of the ocean which now divides this island 

 from the continent did not then exist as a harrier to the migraliun of the 

 mastodons, liippopoiamuses, bisons, bears, ^c, which have left such 

 abundant traces of their former existence in the superficial deposits and 

 caves of Great Britain. Now it is a most interesting fact, that in the 

 Europa;o-Asialic expanse of dry laud species continue to exist of nearly 

 all those genera which are represented by pliocene and post-pliocene mam- 

 malian fossils of the same natural continent and of the immediately adja- 

 cent island of Great Britain. 



Arncrica. 



If we turn our atlenlion to a more distant natural continent — South 

 America, for example — ue shall find that at the present day South Amer- 

 ica ahme, is inhabited by species of which no fossil remains have yet been 

 discovered in Europe, Asia, or Africa. In South America not a single 

 fossil is referable to a true old world mus, though numbers of the common 

 rat and mouse have been imported into South America since its discovery 

 by Europeans. 



In North America the most abundant mammalian fossils of the corre- 

 sponding recent geological epoch belong to a species of mastodon (il/. gi- 

 gunteus) peculiar to that continent. Since, however, North America bor- 

 ders closely upon Asia at its northern basis, aud is connected by its oppo- 

 .site apex with South America, it perfectly accords with the analogies of 

 the geographical relations of the list-extirpated series of mammals of the 

 old world that the Asiatic mammoth and the South Americm megatherium 

 should have migrated from opposite extremes, and have met in the tempe- 

 rate latitudes of North America, where, however, their remains are much 

 more scanty than in their own proper provinces. 



Australia, 



Australia, in like manner, yields evidence of an analogous correspond- 

 ence betvveeu its last extinct and its present aboriginal mammalian fauna, 

 which is the more interesting on account of the very peculiar organisation 

 of most of the native quadrupeds of that division of the globe. The first 

 collection of mammalian fossils from the ossiferous caves of Australia 

 brought to light the former existence on that continent of larger species of 

 the same peculiar marsupial genera; some, as the thylacine, and the da 

 syurine sub-genus represented by the Das. ursiiius, are now extinct on the 

 Australian continent; but one species of each still exists on the adjacent 

 island of Tasmania ; the rest of the fossils were extinct wombats, phalan- 

 gers, potoroos, and kangaroos — some of the latter being of gigantic stature. 

 Subsequently, and after a brief interval, we obtain a knowledge of the 

 former existence of a type of the marsupial group, exemplified by the 

 genera Diprotodon and Nototlierium, which represented the pachyderms of 

 the larger continent, and which seems now to have disappeared from the 

 face of the Australasian earth. 



The most remarkable local existing fauna, in regard to terrestrial verte- 

 brated animals, is that of the islands of New Zealand, with which geolo- 

 gists have been made familiar by HIr. Lyell's indication of its close anal- 

 ogy with the slate of animal life during the period of the Wealdeu forma- 

 tion. The only terrestrial mammalian quadruped hitherto discovered in 



New Zealand, whose recent introduction into that island is at all doubt- 

 ful, is a small rat. The unequivocally indigenous representatives of the 

 warm-blooded vertebra'a are birds, of which the apteryx is the most pe- 

 culiar. It is the smallest known species of the struthious or wingless 

 order, has the feeblest rudiments of the anterior members, and not any of 

 its bones are permeated by air-cells. This bird forms the most striking 

 and characteristic type of the proper or primitive fauna of New Zealand. 

 Not a trace of a fossil quadruped has been found in New Zealand ; but 

 our present knowledge of the living and the last-exterminated faunae of 

 the warm-blooded animals of that small but far-distant and isolated por- 

 tion of earth, shows that the same close analogy existed betwen iliem as 

 has been exemplified in the corresponding faunjE of larger natural divi- 

 sions of the dry laud on the present surface of this planet. 



These Animals cannot hate been derived from a common Asiatic centre. 



Thus the facts obtained from a study ol the fossil remains of mamma- 

 lian quadrupeds, apjilied to a scientific consideration of the present distri- 

 bution of the highest organised and last-created class of animals, demon- 

 strate that, with extinct as with existing mammalia, particular forms were 

 assigned to particular provinces, or natural divisions of the dry land of 

 this globe; and what is still more interesting and suggestive, that the same 

 forms were restricted to the same provinces at the pliocene period as they 

 are at the present day. In pursuing the retrospective comparison of re- 

 cent mammals to those of the eocene and oolitic strata, in relation to their 

 local distribution, we obtain indicationsof extensive changes in the relative 

 position of sea ai^d land during those epochs, in the degree of incongruity 

 between the generic forms of the mammalia which then existed in Europe, 

 aud any that are now found on the great natural continent of which Europe 

 forms part. It would appear, indeed, from our present knowledge, that 

 the further we penetrate into time for the recovery of extinct mammalia, 

 the further we must go into space to find their existing analogues. To 

 match the eocene palteotlieres and lophiodons, we must bring tapirs from 

 Sumatra or South America, — we must travel to the autipodes for myrme- 

 cobians and dasyuies, the nearest living analogues to the amphitlieres and 

 phascolotheres of the ancient oolites. From what ancient centre, if any 

 the first types of the primary groups of the class mammalia may have 

 radiated, we seem ever destined to remain ignorant, by reaj-on of the enor- 

 mous alterations of land and sea that have come to pass since the class 

 was first introduced into our planet. Me find, however, that from the 

 period when the great masses of dry land assumed the general form and 

 position that they now present, the same peculiar forms of manimalia cha- 

 racterised their respective fauna?. If we carry our retrospect no further 

 back than the pliocene tertiary period, the evidence of the distribution of 

 the recent and extinct mammalia would justify the conclusion that New 

 Zealand, Australia, Souih America, and the old world or the geographei-s, 

 had been as many distinct centres of creation. The difficulties that beset 

 the commonly received view are insurmountable. According to the hypo- 

 thesis that all existing land-animals radiated from a common Asiatic centre 

 within the historical period, we must be prepared to admit that the noctur- 

 nal apteryx, which can neither fly nor swim, migrated across wide seas 

 and found its sole resting-place in the island of New Zealand, where alone 



the remains of similar vvingless birds have been found fossil; that the 



wombats, dasyures, and kangaroos should have as exclusively travelled to 

 Australia, where only have been found, in pliocene strata and bone caves 

 the remains of extinct and gigantic species of the same genera or families 

 of maisupialia ; and that the modern sloths, armadillos, and anteaters, 

 should have chosen the route to South America, where only, and in the 

 warmer parts of North America, are to be found the fossil remains of ex- 

 tinct species of those very peculiar edentate genera. It is not less striking 

 and suggestive, though at fir=t sight less subversive of the recent-dispersioQ 

 theory, to find the elephant, rhinoceros, hippopotamus, hyena, beaver, 

 pika, hare and rabbit, vole and mole, still restricted to that great natural 

 division of dry land to which the fossil remains of the same genera or spe- 

 cies appear to be peculiar. 



Mr. Lyell's Lecture cm the Mississippi Delta. 



Mr. Lyell delivered an evening discourse on the delta and allnvial 

 deposits of the Mississippi, and other points in the geology of North 

 America, observed in the years 1845-6. The delta of the Mississippi may 

 be defined as that part of the great alluvial plain which lies below or to the 

 south of the branching off of the highest arm of the river, called the 

 Atchafalaya. This delta is about 13,000 square miles in arrear, r.nd elevated 

 from a few inches to ten feet above the level of the sea. The greater part 

 of it protrudes into the Gulf of Mexico, beyond the general coast line. J he 

 level plain to the north, as far as Cape Girardeau, in Missouri, above the 

 junction of the Ohio, is of the same character, including, according to Mr. 

 Forshay, an area of about 16,000 square miles, and is therefore larger than' 

 the delta. It is very variable in width from east to west, being near its 

 northern extremity, or at the mouth of the Ohio, 50 miles wide, at Memphis 

 30, at the mouth of the White Kiver 80, and contracting again farther south, 

 at Grand Gulf, to 33 miles. The delta and alluvial plain rise by so gradual 

 a slope from the sea as to attain, at the junction of the Ohio, a distance of 

 800 miles by the river, an elevation of only 200 feet above the Gulf of 

 Mexico. 



Mr. Lyell first described the low mud-banks cnvered with reeds at the 

 mouths of the Mississippi, and the pilot-station called the Balize,then passed 

 to the quantity of drift-wood choking up some of the bayons, or channels, 



