XCll THE PALEONTOLOGY OF MINNESOTA. 



Minneapolis and St. Paul. Here we frequently meet with thin slabs, one s de of which 

 may be filled with good specimens of a small variety of Rhynchotrema minnesotensis, Orthis 

 deflecta, Strophomena filitexta, Rafinesquina minnesotensis and Leperditia fabulites. Perhaps 

 ten or twelve othe^ species have been observed in this bed at St. Paul and Minne- 

 apolis that may be considered as common, while all the others are rare. It is to be 

 noticed also that very few, if any, of the common species are limited to the bed, but that 

 nearly all of them are quite as abundant in the succeeding beds of limestone. For this 

 reason no paleontological designation is proposed. 



Vanuxemia bed. This designation is proposed for the upper part (about twelve feet) of 

 the limestone series at St. Paul and Minneapolis. It is in part equivalent to the ' ' Lower 

 Blue limestone " of Wisconsin. The upper five feet are full of fossils, preserved, however, 

 chiefly as empty molds and casts. Still, on the bed planes, Brachiopoda and other shells, 

 as well as trilobites, are often very well preserved. Leperditia fabulites, Rajlnesquina min- 

 nesotensis, Orthis tricenaria, Glathrospira subconica, Trochonema beloitense, Lophospira con- 

 radana, L. serrulata, and Vanuxemia dixonensis are very abundant, and the last four highly 

 characteristic of the bed. Vanuxemia obtusifrons, V. sardesoni, Maclurea depressa, Helicotoma 

 umbilicata, Conradella triangularis, and Gyrtometopus scofieldi, also are characteristic but 

 much less common. 



In giving "Formation and locality" of fossils described in this volume, these two 

 limestone beds are, as a rule, not separately referred to. It is to be understood, therefore, 

 that the designations "Trenton limestone" and "lower limestone of the Trenton forma- 

 tion," may mean either one or both beds. 



Stictoporella bed. This term applies to the ten feet of shale and limestone ("lower 

 third of the Trenton shales") resting on the Vanuxemia bed at St. Paul and Minneapolis. 

 Here it is a well marked horizon, containing an abundant fauna of which Bryozoa are the 

 principal element, no less than thirty-nine species of this class being represented. 

 Stictoporella frondifera, S. anguaris, Pachydictya frondosa and Anolotichia impolita are always 

 abundant and, as far as known, are to be found only in this bed. Among the interesting 

 fossils is a fine new species of starfish, of which three specimens, the largest four inches 

 across, were found at Minneapolis. 



The great abundance of Bryozoa, and the fact that nineteen of the thirty-nine species 

 pass on into succeeding beds might be considered as good evidence for uniting the Sticto- 

 porella bed with the next group rather than with the Stones River group. But this would 

 be an error since it is clearly nothing more than the upper member of the Stones River 

 group, which, in tracing it northwestward from Beloit and Janesville, Wisconsin, where it 

 cannot be distinguished from the "Lower Blue limestone,'' gradually becomes more and 

 more shaly. The conditions seem to have been eminently favorable for the development 

 of bryozoan types, so it might be expected that many species would be ushered in, that, in 

 this region, reached the night of their development first in the upper part of the next bed. 

 The same intimate faunal connection with the succeeding beds is exhibited also by some 

 of the other classes of fossils. As shown in the list nearly 44 per cent (42 of 96) of its 



