1(>2 Reviews. 



lowest beds of the Tongrian System appear as the base of the whole 

 marine tertiary formation of the North of Germany, to the total 

 exclusion of all older formations, this is an important geological 

 support to the view of Sir C. Lyell, that a stronger line of separa- 

 tion is to he drawn between the Laeken and Tongrian systems 

 rather than between the Tongrian and the Rupelmonde systems ; 

 but he does not agree with Lyell in giving to these united systems 

 the name of Upper Eocene rather than Lower Miocene — he rather 

 adopts the views of the French Palaeontologist in considering 

 them the forerunners of the Miocene formation, and is therefore 

 prepared to call them Lower Miocene. 



After alluding to the different suggestions of Dumont and others 

 for various subdivisions of the tertiary formation, he observes, 

 (while at the same time refusing to be bound to the mere artificial 

 rule of percentages), that the terms Eocene, Miocene, and Pliocene, 

 should be maintained as representing periods of time, the centres 

 of which are well known to us, but whose beginnings and ends 

 run into each other ; in the same way as, the more our knowledge 

 is extended, we find to be more and more the case in all investiga- 

 tions respecting geological periods. 



In conclusion, the author adds a few words respecting the ar- 

 rangement and the form in which he proposes to give his descrip- 

 tion of the north German tertiary shells. The Univalves precede the 

 Bivalves ; and adopting the plan of Hbrnes's work on the Vienna 

 Basin, he commences with the Gastropods. This has the advan- 

 tage of establishing a more easy system of comparison between the 

 two formations ; and with the same highly laudable view he has 

 determined to adopt the same order of genera. This is the more 

 praiseworthy, as he admits that in some instances a more satis- 

 factory arrangement might have been adopted. Such a sacrifice 

 of personal views is the more to be admired in proportion as it is 

 rare ; and the advantage to students of the two systems cannot be 

 questioned. He has wisely determined not to overload his work 

 with too much description, or the useless repetition of synonyms 

 already published in so many other standard w r orks. 



To give some idea of the extent of the work, we add a list of 

 the genera already published, with the number of species belong- 

 ing to each, genus : — Voluta, 10 species ; Mitra, 11 ; Oolumbella, 

 3 ; Terebra, 6 ; Buccinum, 13 ; Purpura, 2 ; Cassis, 7 ; Cassida- 

 ria, 3 ; llostellaria, 2 ; Aporrhais, 2. Total, — 60 species on 15 

 plates. 



We cannot conclude these remarks without thus publicly award- 

 ing our thanks to Prof. Beyrich for having undertaken this work. 

 It is evident that we can have no correct idea of the real nature of 

 the successive fades of the Molluscan fauna of the Northern 

 Oc an without it. It will indirectly tend to give us more correct 

 views of our own interesting tertiary formations, and thus lead to 



