C. Schuchert — Russian Carboniferous and Permian. 43 



the transgression were younger than those of the pivotal region. 

 In transgressions, one has to calculate not only with two dimen- 

 sions, but also with a third, because a species may occur in 

 geologically older beds near the center than at the periphery, 



where it may be found unchanged in younger deposits 



It may be assumed that at the time of the Upper Carboniferous 

 iu the region of the present Urals, there existed an extended 

 ocean, whose boundary was pushed toward the south and 

 southeast ( Uralic transgression ). This transgression was not 

 of a catastrophic or sudden nature, but was slow and continuous 

 through along period of time. The fauna spreading with the 

 transgression passed, at least in part, unchanged into younger 

 deposits ; while in the outermost boundaries of the transgres- 

 sion, in the Salt Range and in the Himalaya, there occurs a 

 series of forms in beds that are younger than the same species 

 found in the central region. This crudely stated hypothesis 

 naturally collides, of course, with the theory of guide-fossils 

 ( Leitfossilien ), but my long-continued studies in India, namely, 

 in respect to the Tertiary fauna, have more and more convinced 

 me that the rigid theory of guide-fossils, valuable as it is within 

 restricted areas, always proves disappointing when applied to 

 greater, more widely extended regions." 



In the author's larger work of 1901, cited above (4), he fully 

 presents his views regarding the sequence of the Indian Permian 

 and Triassic sections and their correlation with that of Europe. 

 Xoetling, however, recognizes that the difficulties are great, 

 for he states : u If the Permo-Triassic formations of the Salt 

 Range had first been studied, it would never have occurred to 

 anyone to draw a line in this unbroken series and to apply to 

 the divisions two names. One would have regarded the series 



as a unit, which it is If from these formations one had 



proceeded to seek the European equivalents, they would have 

 been hard to force into the scheme framed for the Salt Range. 

 Speculation of every sort would probably have been resorted to. 

 I now find myself in an analogous position in forcing into the 

 European scheme the Permo-Triassic series of the Salt Range, 

 and if it is to be employed in this case then one must make a 

 purely artificial separation " (4, p. 458). 



From this work, the table of Plate I is compiled, giving the 

 sequence of the formations, their termiuology, thickness, and 

 correlations with European standards ; the Himalayan section 

 is added from Xoetling's paper here numbered 3. 



The second of these papers cited deals with the very impor- 

 tant Permian ammonite Medlicottia. The genus is here 

 studied in considerable detail and comparisons are made between 

 the EurojDean and Indian species. The American forms are 



