Reviews — Prof. A. Hyatt — Genesis of the Arietidce. 325 



the superincumbent water. He further compares the rocks with 

 those of other ages, from the prepaleeozoic downward, and is very 

 emphatic as to the impossibility of using age as a character in any 

 natural or logical classification. 



§ 8. The relations of the rocks to the sedimentary deposits. Prof. 

 Stefani proved in 1876 that the serpentine of Garfagna was 

 regularly interstratified in the Upper Eocene ; this has been sup- 

 ported by Taramelli, and may be regarded as a type case. Sterry 

 Hunt's view that the serpentines are part of a prepalseozic floor 

 exposed at places by denudation, etc., is very summarily dismissed : 

 " It is the opinion of one, who either does not observe facts or, who 

 having observed them, gives more weight to his own conceits than 

 to these." The author has discussed this hypothesis once before, 

 and does not seem to deem it necessary to repeat the process. 



§ 9. The most important point established in the section on dis- 

 tribution is that there is as a rule a fairly constant succession; the 

 peridotites were the earliest, the gabbros followed, and the diabases 

 concluded the series. But in places diabase occurs intercalated in 

 either the peridotite or gabbro, and these with otber exceptions show 

 that the rule is not absolute. 



In conclusion, the author refers to the extension of similar eruptive 

 rocks of the same age, along the northern coast of the Mediterranean ; 

 these can be traced in Spain, Switzerland, Dalmatia, and through 

 Bosnia and Herzegovina, as far south as Euboea. The opinion is 

 advanced that in late Eocene times, these rocks were erupted from 

 a series of volcanoes, often submarine, that encircled the northern 

 margin of a very deep sea, just as the Malayasian volcanoes extend 

 along the northern margin of a deep part of the Pacific. 



Though many geologists will probably require further evidence 

 before accepting some of the author's conclusions, such as that the 

 division into plutonic and volcanic is fundamentally erroneous, that 

 the gabbros are eruptive, or that the " serpentine breccias " are 

 " tuffs," they cannot but be grateful to Prof. Stefani for so valuable 

 a contribution to so intei'esting a group of rocks, and will await 

 with interest the promised publication of the issues of his further 

 investigations. J. W. G. 



II. — The Genesis of the Akietid^. By Professor Alphetjs 

 Hyatt. Smithsonian Contributions to Knowledge, 673. 4to. 

 pages vii-xi, 1-223 ; 14 Plates and 35 Woodcuts. (Washington, 

 1889.) 



THE handling of a collection rich not only in species but in all 

 possible varieties and abnormal forms, and access to the 

 literature upon the subject, are important factors in genealog'ic 

 investigations. Such opportunities has Prof. Hyatt enjoyed, and his 

 latest work just to band is another proof that he has turned them to 

 the best possible account. 



Since 1867 Prof. Hyatt has given to the world a most valuable 

 series of pamphlets concerning the genealogy and classification of 



