NA TURE 



537 



THURSDAY, SEPTEMBER 19, 1878 



THE LINKS OF THE ANIMAL WORLD 

 Les Enchainements dii Monde Animal dans hs Temps 

 Ghlogiqties, Mammijlres, Tertiares. Par Albert 

 Gaudry. 8vo. (Paris : F. Savy, 1878.) 



UNDER this poetic title Prof. Gaudry has added one 

 more to his valuable works on the fossil mam- 

 malia of the Tertiary Period. Some sixteen years ago he 

 carried on the explorations on the classic ground of 

 Pikermi, which proved that the plains of Marathon were 

 haunted by antelopes, gazelles, giraffes, and hipparions, 

 in the upper miocene age, while the forests then over- 

 shadowing rocky Attica sheltered the mastodon and 

 rhinoceros, and yielded food to innumerable monkeys 

 (Mesopithecus) allied to the Barbary ape. During the 

 last five years he has been painting a like picture of the 

 upper miocene mammalia of Mont Ldberon, in which, as 

 in Pikermi, the remains of the ani.nals are preserved in 

 an abundance and a perfection somewhat like those 

 discovered in the Western States, by Prof. Marsh. The 

 two elaborate quartos on these discoveries are now fol- 

 lowed by an elegant octavo full of woodcuts, treating of the 

 links that bind together some of the more important groups 

 of tertiary and living mammalia. In it the author deals 

 with the European mammalia without treating exhaustively 

 the accumulation of facts brought to light by Marsh, 

 Hayden, Leidy, and others, in the American eocenes and 

 miocenes. Norare these as yet published in sufficient detail 

 to allow of their being worked into the book before us. 

 The impression made upon my mind by the vast stores 

 of remains in the museum at Yale is one of profound 

 melancholy ; for so numerous and varied are the mam- 

 malia that many years must elapse before they can be 

 brought into complete relation with those of Europe. 

 Up to the present time the fragmentary notices which 

 have appeared bear the same relation to the systematic 

 treatment to be expected from Prof. Marsh, that isolated 

 tessera: bear to the whole design of a mosaic. Prof. 

 Gaudry, therefore, has acted well in confining his work 

 mainly to the Tertiary mammalia of Europe. 



Our author approaches his subject from the point of 

 view offered by evolution, by taking some of the more 

 salient characters of a group, and tracing their " descent 

 with modification," in passing from older to newer stages 

 of the geological record. The fishes passed through the 

 principal phases of their evolution in the Primary, the 

 reptiles manifested their most extraordinary modifica- 

 tions in the Secondary age, and at its close had settled 

 down into that equilibrium which they now present, 

 while the mammalia were being unfolded, form 

 after form — "en pleine Evolution "— in the Tertiary 

 Period. In the opening chapter the relation of the 

 marsupials to the placental mammals is discussed, and 

 our author concludes, from the results of embryology, 

 that the former must have preceded the latter, and that 

 the imperfect and helpless condition of the young, 

 nourished in a marsupium, or taking refuge on the back 

 of the mother, would be a serious obstacle to rapid in- 

 crease, since the young would be likely to be drowned in 

 the passage of rivers or arms of the sea in migration in 

 Vol. XVIII. — No. 464 



search of food. This may have been j)ne of the causes 

 of their being supplanted by the placental mammals at 

 the beginning of the Tertiary Period, as they would be 

 heavily weighted in the struggle for life by this condition. 

 The elimination of the marsupial herbivora from the 

 Tertiary fauna of Europe and America might have been 

 produced by the migration rendered necessary by the 

 great geographical and climatal changes at the close of 

 the cretaceous age. It is a significant fact that the only 

 living mammalian genus found in the eocene age is the 

 tree-haunting Didelphys, which took refuge probably in 

 the forests, and held its place in Europe as late as the 

 lower miocene age, and which still holds its own in the 

 warmer parts of America as the sole representative of a 

 Secondary marsupial fauna once in possession of the 

 European and American continents. There are, how- 

 ever, traces of a marsupial fauna other than those offered 

 by Didelphys, to be seen in certain intermediate forms. 

 The Hyzenodon of the eocene and lower and middle 

 miocene, and the eocene Pterodon, were carnivores com- 

 bining the dental formula of four true molars (three of 

 which are carnassials), and three premolars of the 

 Thylacinits, with the characters of an ordinary placental 

 carnivore. The dentition of the lower eocene Palseonictis 

 is remarkably like that of the Tasmanian Dasyure, and 

 the lower miocene Proviverra unites a marsupial denti- 

 tion and brain with the ordinary viverrine attributes. 

 These marsupial characteristics can only be accounted 

 for on the hypothesis that they have been handed down 

 from a marsupial ancestry, and they render the conclusion 

 highly probable, that all the placental are descended 

 from the implacental carnivores. 



Prof. Gaudry points out that the rhinoceros and the 

 palseothere are probably descended from common 

 ancestors, and shows the gradual modification of 

 skull, and evolution of horns in the former animal. In 

 the middle miocene a hornless rhinoceros (Aceratherium) 

 appears, and is accompanied in the upper miocenes of 

 Eppelsheim by a small horned species, of which it is 

 probably the female. As we pass upwards to the pliocene 

 the horn becomes more highly developed, and the nasal 

 bones more strongly built, until we arrive at a maximum 

 in the pleistocene Rhinoceros tichorhinus. AVe believe 

 that the horn was originally a male character transferred 

 ultimately to the female in the way pointed out by Mr. 

 Darwin. 



In like manner, also, our author traces the evolution 

 of horns and antlers in the ruminants. The earliest 

 representative of the order, if it be a representative, is 

 the hornless Xiphodon of the upper eocenes. Horns 

 come in in the middle miocene, and in the upper 

 attain a considerable development, as in the antelopes. 

 We may add that, in Europe, the bovine development of 

 horns arrived at its maximum in the gigantic bisons and 

 uri of the pleistocene, while in the pliocene of Italy 

 there was a bos without any horns — a fact which rendiers 

 it probable that the polled cattle produced by domestica- 

 tion is merely a case of a reversion to an ancestral typa^ 

 fostered by the care of man. None of the lower mio- 

 cene deer possessed antlers. In the middle miocene* 

 they are bifurcated, as in the Muntjac; in the upper 

 they are still small, and with three or more types ; in the 

 pliocene they pass through the stages presented by the 



