REVIEWS 101 



Mr. W. N. Logan who has done much toward giving us a clear con- 

 ception of the stratigraphic relations of the Upper Cretaceous, presents 

 an excellent discussion of the invertebrates of the Benton, Niobrara, and 

 Fort Pierre groups. He not only reviews the species hitherto described, 

 but adds the descriptions of many new ones which he has found. 

 His work is admirably arranged, and the species so tabulated, that the 

 whole forms a convenient paper of reference. It is to be hoped that 

 much more work of this kind may soon be done in the great Interior 

 Cretaceous region, that a more definite knowledge of its rich inver- 

 tebrate fauna may be available. 



W. T. Lee. 



