614 



NA TURE 



[Oct. 



o> 



1888 



to say that this jaw does not belong to Amphitherium — 

 it very probably does ; but it certainly does not afford 

 decisive evidence on which to base an extensive super- 

 structure, and to make Amphytherium the type of one 

 family, while Amphitylus and Amphilestcs (regarded by 

 Owen as closely related to the former) are referred to the 

 Triconodonlidtc. Then, again, exception may be taken 

 to the interpretation of the molar structure in the jaw in 

 question. Prof. Osborn regards the teeth as consisting 

 of two cusps and a talon in line, approximating to the 

 fashion of A mphi testes ; but to us they appear to re- 

 semble those of the Upper Jurassic genus Amblolhc- 

 rium, in which the molars consist of a trilobed blade 

 and a posterior talon. Now, Amblotkerium is made the 

 representative of a family which is taken as the type of 

 the Insectivora Primitiva. Apart from the question of 

 what Amphitherium really is, the molar teeth of Ambto- 

 therium, as already said, differ considerably from those 

 of Amphilestcs (Prodidelphia) ; but, since precisely ana- 

 logous differences occur n a single family of existing 

 Marsupials, these differences do not appear to afford 

 grounds for even family, let alone ordinal, distinction. 

 No definite characters are, indeed, given by which the 

 Insectivora Primitiva (p. 235) are to be distinguished 

 from the Prodidelphia ; and if we compare the figure of 

 the mandible of Amphilestcs, given on p. 228, with that 

 of Amblothcrium, represented in Plate ix., Fig. II, the 

 resemblance in the contour of the posterior portion of 

 the jaw is so close that scarcely even generic distinction 

 could be drawn from this part. The conclusions drawn 

 from this portion of the jaw in the diffeient forms are 

 indeed very remarkable. Thus we have already noticed 

 how the low condyle is given as a character of the 

 Tritylodontida, and yet the feature is totally wanting 

 in the first genus, Amphitestes, which agrees exactly with 

 Amblotlicrium in its lofty condyle. The alleged broad 

 and narrow coronoids of the two forms may be in great 

 part due to the effects of pressure. The absence of in- 

 flection in the angle of Amblotherium is shared by some 

 of the forms included in the Triconodontidce. Then, 

 again, we are totally unable (after repeated examinations 

 of the types) to see how the lower jaw, on which P era- 

 spat ax was founded, can be even generically distin- 

 guished from Amblotherium, the dental formula being, 

 with the exception of an additional lower molar, identical ; 

 and yet the one genus is referred to the Prodidelphia, 

 and the other to the Insectivora Primitiva. As another 

 instance, the general similarity in the structure of the 

 lower molars of Spalacotherium to those of Chrysochloris 

 coupled with an analogous similarity existing between the 

 upper ones of Peralestes and those of the same existing 

 genus, suggests at all events a very considerable presump- 

 tion that the two fossil genera may be identical. We find, 

 however, Spalacotherium placed in the Triconodontidcr, 

 while Peralestes is made the type of another family of the 

 Prodidelphia, which includes the above-mentioned Pera- 

 spalax. Now, even if the above obvious resemblance is 

 ignored, we totally fail to see any reason for including 

 Spalacotherium in the Triconodontidce, and agree with 

 Prof. Marsh in regarding it as the type of a distinct 

 family. If, moreover, any of these forms are to be 

 referred to the Insectivora, we should have thought that 

 Spalacotherium, with its Chrysochloris-hke molars, and 



the reduction of its lower incisors to the Eutherian three, 

 was the very one which had a claim to such a position. 

 In regard to the new genus Kurtodon — the type of the 

 Kurtodontidce — we can only say that. there appears to us 

 to be no evidence that the upper jaws on which it is 

 founded may not belong to one of the genera named on 

 the evidence of the mandible. 



Other points might be noticed if space permitted ; 

 but we have indicated enough to show that a great 

 deal more must be absolutely proved before many 

 of the genera admitted by Prof. Osborn can be even 

 allowed to stand as definitely distinct ; while, as to 

 the proposed division of the Polyprotodont forms into 

 Insectivora and Marsupialia, we have shown that in its 

 present form it breaks down hopelessly at every point, 

 although we are far from saying that all the known forms 

 are certainly Marsupial. It appears, however, desirable, 

 till we attain much fuller knowledge of their organization, 

 to leave a large proportion of them in a single ill- defined 

 family. 



In criticizing this memoir we have not hesitated, in 

 what appear to us to be the true interests of science, to 

 speak freely. We should, however, be unjust if we 

 failed to recognize the amount of labour of a very try- 

 ing kind which the author has bestowed on the subject ; 

 and we especially commend the value of his observations 

 on the Multituberculata. It is also a decided advantage 

 ' to have all the American and European forms compared 

 ! together by one who has had the good fortune to study 

 ' so many of the types from both areas. Finally, no one 

 1 can fail to be struck with the excellent illustrations with 

 which the monograph is adorned, a large number of 

 which, we believe, are from the author's own drawings. 



EA R TH SCULP TURE. 

 Les Formes du Terrain. Par Lieut. -Colonel G. De la 

 Noe, avec la collaboration de Emm. de Margerie. 

 2 Vols. (Text, pp. 205 ; Plates xlix). (Paris, 1888.) 



THE origin of the features of the earth's surface must 

 always prove an attractive subject no less to the 

 geographer than to the geologist. The one describes and 

 the other expounds ; and the work before us is an admir- 

 able example of what may be done by the joint labours of 

 geologist and geographer in illustrating and explaining 

 the form of the ground. 



In turning over the pages of the work, and in contem- 

 plating the many instructive diagrams and pictorial illus- 

 trations, one is prepared for a more exhaustive treatment 

 of the origin of scenery than is really to be found in these 

 volumes. So far as the geologist is concerned, the work 

 is mainly a treatise on sub-aerial denudation, and with 

 special reference to France. It is almost entirely occupied 

 with the method of denudation by rain and rivers, and with 

 an account of the features which they originate. We are 

 told how different rocks are disintegrated by surface 

 agencies, and how the broken material is afterwards 

 transported by streams. Attention is especially called 

 to the action of running water on rocks of varying cha- 

 racter and inclination, to the influence of vegetation in 

 preserving slopes at certain inclinations, and to the effect 

 of rain in diminishing the angle of slopes. The influence 

 of climate is dwelt upon, and it is shown how the perme- 



