568 Reviews— Prof. W. B. Scott— On Oreodo'ts. 



fissure ; he inaugurated the study of extinct volcanoes dissected, so 

 to speak, by the processes of denudation ; and he seems to have 

 been the first to form clear ideas as to the true relations existing 

 between the crystalline igneous rocks of a district and their asso- 

 ciated lavas. In short, " while much that is new and valuable has 

 been contributed to geological science by more recent investigations, 

 and many changes have been made in nomenclature and other points 

 of detail, it is interesting to find that all the chief facts described 

 by Darwin and his friend Prof. W. H. Miller have stood the test of 

 time and further study, and remain as a monument of the acumen 

 and accuracy in minute observation of these pioneers in geological 

 research." 



Darwin's " Geological Observations on South America " is a work 

 that seems to have hitherto attracted less attention than either of the 

 foregoing. Prof. Judd, however, is inclined to believe that the 

 researches here detailed will eventually be regarded as one of the 

 author's chief titles to fame. It was in this volume that. Darwin 

 first emphasized the imperfection of the geological record ; at the 

 same time enunciating the important conclusion that each great 

 geological period has exhibited a geographical distribution of the 

 forms of animal and vegetable life, comparable to that which 

 prevails in the existing fauna and flora. It was here, too, that uni- 

 formitarian views on the volcanic phenomena of past ages were first 

 clearly expounded, with abundant illustrations. Finally, Darwin's 

 study of the schists and gneisses of South America led to the earliest 

 recognition of the intimate relationship existing between planes of 

 foliation and thrusts during elevatory movements — thus anticipating 

 some of the most recent conclusions deduced from researches among 

 the metamorphosed rocks of Scotland, Norway, Saxony, and other 

 areas. 



The volume is provided with a good index of 30 pages, and will 

 be one of the most welcome additions to a working geologist's library 

 that has appeared for some time. 



II. — Prof. W. B. Scott on the Oreodonts. 



Beitrage zdr Kenntniss der Oreodontid.^;. By W. B. Scott. 

 Morphol. Jahrbuch, Vol. XVI. Part 2. Illustrated. (1890.) 



THIS memoir is a very valuable contribution to our knowledge 

 of that remarkable family of North American Artiodactyle 

 Ungulates commonly known as Oreodonts, in which the author 

 gives in a concise form all the important features of their osteology. 

 Judging, indeed, from the skeleton represented in the first of the 

 plates accompanying the memoir, it may be inferred that our 

 knowledge of the skeletal anatomy of the type-genus of the family 

 is now practically complete, and as well known as that of existing 

 mammals. The remarkable variations exhibited by the skulls of 

 the different genera are admirably illustrated in the other plates ; 

 and we may especially call attention to the tendency to the develop- 

 ment of facial vacuities in the skulls of the more specialized forms. 



