CV1 THE PALEONTOLOGY OF MINNESOTA. 



The total number of species and varieties in the Lower Silurian, belonging to the 

 classes studied, which have been discussed in the volume, is eight hundred and eighty-one, 

 and of these six hundred and ninety- three have been identified in the state, and ninety 

 have been obtained from other states, and are likely to be found in Minnesota. They are 

 distributed as follows: 



Sponges. 11 species, of which one only has been found in Canada. 



Graptolites. 3 species, all of which have been found in New York and Canada. 



Corals. 10 species, of which 4 have been found in New York and Canada. 



Bryozoans. 162 species, of which 15 are in New York and Canada, and 17 have not been 

 found in Minnesota. The 19 large genera, i. e., those containing four or more species are 

 the following: 



Stomatopora 4 species. Monticulipora 5 species. 



Bhinidictya 9 species. Atactoporella 4 species. 



Pachydictya 7 species. Homotrypella 6 species. 



Escharopora 4 species. Homotrypa 8 species. 



Stictoporella 6 species. Prasopora 8 species. 



Helopora 7 species. Mesotrypa 5 species. 



Artbroclema 5 species. Callopora 9 species. 



Nematopora 4 species. Batostoma 8 species. 



Phylloporina 4 species. Monotrypa 4 species. 



Leptotrypa 4 species. 



Of this total 9 species have not yet been found in Minnesota, leaving 102 species in 19 

 genera, which are known to occur within the state. The other 30 genera, of which one 

 (Heterotrypa) does not occur in the state so far as known, contain 51 species. 



Brachiopods. 81 species, of which 20 species (and 2 varieties) occur in New York, and 

 33 species (and 4 varieties) occur in Canada. There is a total of 40 species common to 

 Minnesota, New York and Canada. Of the 81 species considered, 8 are not found in the 

 state, making a total of 73 species of known Lower Silurian brachiopods. The large 

 genera, having each four or more species, are: . 



Lingula 12 species. Strophomena 12 species. 



Orthis 17 species. 



Of these 3 are not found in Minnesota, leaving 38 species in 3 genera. The other 24 

 genera contain 40 species. Two of these (Schizambon and Rhynchonella) have not been 

 found in the state. 



Lamellibranchs. 131 species, of which 18 are not found in Minnesota, 7 are in New 

 York (and Penn. ), and 5 in Canada. Nine species are common to Minnesota, New York 

 and Canada. 



The large genera, i. e., those containing 4 or more species, are the following: 



Ambonychia 4 species. Cyrtodonta 16 species. 



Clionychia 5 species. Vanuxemia 15 species. 



Modiolopsis 11 species. Whitella 12 species. 



Orthodesma 4 species. Ctenodonta 26 species. 



Endodesma 5 species. Technophorus 4 species. 



Of these 15 are not found in Minnesota, leaving 87 species of Minnesota lamellibranchs 

 in 10 genera. The total number of genera is 27. The other 17 genera contain 29 species. 



