Notices respecting New Books. 315 



fresh slices to his domain carved out of his rival's territory, so 

 that ultimately his Silurian embraced every thing of the Old G-rey- 

 wacke save a few barren slates. 



Considering that the present work is a Sedgwick Prize Essay 

 written by a distinguished young geologist, who has made the 

 Lower Palaeozoic Eocks his especial study, it is not surprising that 

 he should have accepted a brief for the plaintiff in the great case 

 of Sedgwick v. Murchison, and that he should regard all compromise 

 in a suit, which seems likely to be transmitted from generation to 

 generation, as only throwing the nomenclature into worse confu- 

 sion. Mr. Marr is, in fact, on this occasion the exponent of the 

 views of the Cambridge School, which also find an able advocate in 

 the eloquent successor of Sedgwick who now fills the Woodwardian 

 Chair. These men are determined that justice shall be done, 

 though late, to the illustrious author of the Cambrian System. 



In his introduction the author clears the ground, as it were, by 

 indicating what he considers to be the principles of classification ; 

 and, moreover, points out the errors arising from field geologists 

 having formed lists of fossils belonging to certain series, which 

 contain some wrong determinations, whereby the number of fossils 

 apparently common to two different systems may be increased. 

 Then follows a dissertation on the position of the boundary-liae 

 between the Cambrian and Silurian Systems, which the author 

 considers to be marked by a strong unconformity in most areas. 

 And here it should be noted that the Silurian System is for him 

 more or less coincident with the Upper Silurian of the Geological 

 Survey, whilst his Cambrian System includes the rest of the Lower 

 Palaeozoic beds down to the pre-Cambrian rocks. He then gives a 

 brief description of the Cambrian and Silurian Eocks of the British 

 Isles, followed by a further description of their occurrence on the 

 European continent and in America. These descriptions are 

 fortified by numerous lists of characteristic fossils, which form no 

 inconsiderable portion of the entire work, and bear witness to a 

 most creditable amount of palaeontological knowledge. A brief 

 conclusion is followed by tables of British and foreign fossils ; but 

 no attempt is made to show the percentage of fossils common to 

 two subdivisions, since the Author considers such tables to be 

 misleading in the present state of our knowledge. 



In order to establish his position the author masses his forces on 

 two points. Firstly, to show that the break at the base of the Silurian 

 (i. e. Upper Silurian) is one of the highest importance ; secondly, 

 to prove that there is no such break in any portion of Sedgwick's 

 Cambrian. 



1. Break between Sedgwick's Cambrian and the overlying Silurian, 

 —It will be remembered that in 1879 Prof. Lap worth expressed 

 his opinion that the local unconformities between the Balas and 

 Llandoveries had been made too much of, and he argued for their 

 being in the main stratigraphically concordant nearly all over the 

 world. But Mr. Marr assures us that he has seen evidence of a 

 physical discord not only in the tvpical area, but also in the North 



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