70 Notices respecting New Books. 



fishes and sauvians, link it more closely to the period of the Zcch- 

 stein, whilst its peculiar plants appear to constitute a Flora of a 

 type intermediate between the epochs of the New lied Sandstone or 

 Trias and the Coal-measures. Hence it is that I hare ventured to 

 consider this series as worthy of being regarded as a system *." 



In subsequent years, having personally examined this group in 

 the typical tracts of Germany as well as of Britain, I felt more than 

 ever assured that, from the great local variations of mineral succes- 

 sion of the grovp, the word " Permian," which might apply to any 

 number of mineral subdivisions, was the most comprehensive and 

 best term which could be used, the more so as it was in harmony 

 with the principle on which the term Silurian had been adopted. 



Apart from the question of the substitution of the new word 

 "Dyas" for the older name "Permian," I take this opportunity of 

 expressing my regret that some German geologists are returning to 

 the use of the term " Grauwacke Formation," as if years of hard 

 labour had not been successfully bestowed in elaborating and esta- 

 blishing the different Palaeozoic groups, all of which, even including 

 the Lower Carboniferous deposits, were formerly confusedly grouped 

 under the one lithological term of the " Grauwacke Formation." 



Eespecting as I do the labours of the German geologists who 

 have distinguished themselves in describing the order of the strata 

 and the fossil contents of the group under consideration, I claim 

 no other merit on this point for my colleagues de Yerneuil and 

 von Xeyserling, and myself, than that of having propounded 

 twenty years ago the name of " Permian " to embrace in one natural 

 series those subformations for which no collective name had been 

 adopted. Independently, therefore, of the reasons above given, which 

 show the inapplicability of the word " Dyas," I trust that, in accord- 

 ance with those rules of priority which guide naturalists, the word 

 "Permian" will be maintained in geological classification. 



London : Belgrave Square. 

 Nov. 30, 1861. 



X. Notices respecting New Books. 



Euclid's Elements of Geometry , designed/or the use of the higher Forms 

 in Public Schools and Students in the Universities. By Robert 

 Potts, M.A., Trinity College, Cambridge. Corrected and Improved 

 edition. London : John W. Parker, Son, and Bourn. 



MR. POTTS' first octavo edition of Euclid appeared in 1845, and 

 since then has been gradually gaining ground in the estimation 

 of our best teachers as one of the most unexceptionable books of its 

 class at present within the reach of the students in our schools and 

 universities. The work is too well known to require description, 



* In my last edition of ' Siluria ' I have spoken of the Permian as the "Upper- 

 most Pakcozoic group, but have not deemed it a system by comparison with the 

 vast deposits of Carboniferous, Devonian, and Silurian age. 



