Geology. 45 7 



shade" (p. 170). The reviewer wishes to say that this conclusion 

 is entirely in accord with the recent studies made of nearly one 

 hundred bogs in Connecticut, in which the role played by peat 

 has been heretofore misinterpreted. 



The chapter on the method of formation of bogs and their 

 distribution contains much that is of interest to physiographers. 



The commercial value of peat, method of preparing it for the 

 market, etc., is discussed in considerable detail. h. e. g. 



4. Illinois State Geological Survey, H. Foster Bain, Director. 

 Bulletin No. 6. The Geological Map of Illinois (Second edition) ; 

 by Stuart Wellek. Pp.32, with map. Urbana, 1907. — The 

 activity of the Illinois Survey is well shown by the fact that a 

 second edition of the geological map has been issued within a 

 year (see this Journal, vol. xxii, p. 543, 1906). Considerable new 

 information is given on the revised map, and in the accompanying 

 bulletin Dr. Weller discusses the formations in the light of 

 recent field work. The outline of the Carboniferous has been 

 entirely revised. h. e. g. 



5. North Dakota Geological Survey. Fourth Biennial Report. 

 A. G. Leonard, State Geologist. Pp. 312, 37 pis., 1 map. Bis- 

 marck, 1906. — The present report is a volume on the clays and 

 clay industry of the state and should serve to increase the esteem 

 with which the Survey is held by the people of North Dakota. 

 The subdivisions of the subject, as treated, are: clay and its 

 properties with special reference to North Dakota, sti*atigraphy 

 of North Dakota clays, economic geology of clays, uses and 

 value of clay products, and methods of brick manufacture. 



H. E. G. 



6. Sur la Fixation des Coquilles de Quelques Strophomena- 

 cea ; by N. Yakovlew. Bull. Comite Geol., St. Petersbourg, 

 xxvi, 1907, pp. 181-201, pis. 3, 4. — From the short French resume 

 one learns that Meekella may be cemented to foreign objects by 

 the ventral beak and grow in clusters with three to four individ- 

 uals lying over one another — the cardinal area of one adjusted 

 over the back of the ventral valve of another individual. When 

 the shells are not cemented the cardinal areas are low and sym- 

 metrical, the valves flattened and the plications regularly devel- 

 oped. In the cemented forms the ventral area is much drawn 

 out and more or less twisted to one side, while the plications are 

 irregularly developed and even obsolete on the lateral parts of 

 the valves. The calcareous cement, the author thinks, is extended 

 through umbonal pores — a probable misunderstanding of the 

 punctate nature of the Strophomenacea. 



The author also states that in Strophalosia and Aulosteges 

 individuals may or may not be cemented by the ventral beak. 

 In these genera the reviewer has seen individuals cemented by 

 the spines, so that the absence of a ventral cicatrix is not final 

 evidence of a lack of cementation. 



Finally the author states that different species of Strophalosia 

 have developed different species of Aulosteges, just as different 



