584 P. E. RAYMOND TRENTON OP TENNESSEE AND KENTUCKY 



Paris, Kentucky, and surmises that it once passed all across the southern 

 part of the arch and has subsequently been removed. This would in- 

 volve uplift and erosion after the Cornishville and before the Cynthiana. 



If, however, the Salvisa be the deposit of a lagoon, it would involve 

 only a shallowing of the water at the end of the Woodburn and sufficient 

 uplift or upgrowth that basins might be formed. In that case the deposit 

 about Paris may not have been connected with the greater one south of 

 Frankfort. 



Lithologically, the Paulconer is a mass of shells such as would be most 

 apt to occur near a shore or on a bank or reef. Furthermore, the transi- 

 tion between the Woodburn and Cynthiana, where there is no Perryville 

 present, is a gradual one, and it is practically impossible to draw a line 

 between the two on lithological grounds. Faunally, the Cornishville 

 above the Salvisa is allied with the Benson and Woodburn rather than 

 the Cynthiana, but the Woodburn and Salvisa contain the earliest of 

 the Cynthiana types. Everything, therefore, suggests a very brief "lost 

 interval" at this horizon. 



The very great difference between the fauna of the Upper Trenton hi 

 Kentucky and that of northern Xew York, Ontario, and Minnesota must 

 be ascribed to geogTaphical conditions. While certain forms were mi- 

 grants, others remained in or near their "center of distribution." The 

 sea was so fully populated in later Trenton times that the animals which 

 were driven westward by the invasion of mud found but inhospitable 

 reception. It may also be noted that the tong-ue of mud which reached 

 Cincinnati was thrust out into the Trenton sea in such a way as to make 

 a northern and southern province, Ottawa on the north and the Cum- 

 berland front in Tennessee on the south, being far to the east of its most 

 westward distribution. In fact, so far as we know from any actual out- 

 crops at the present time, this mud may have formed a complete barrier 

 to migration of shore-inhabiting animals between northern and southern 

 seas in late Trenton and post-Trenton times. 



The proper application of the term Trenton remains to be cleared up, 

 and the discussion of the subject is best deferred until the publication of 

 Dr. Ruedemamr's studies of the Utica and Frankfort shales. It is quite 

 patent, however, that we in America must eventually follow the Euro- 

 peans in eliminating from our time-table any periods which have been 

 based entirely upon the black shale facies. At the present time, as a 

 matter of convenience, I am using Trenton to include deposits dating 

 from the time of the first appearance of Platystrophia, which is usually 

 immediately anterior to the first appearance of Cryptolithus, to and in- 



