1870.] '^"5 [Winchell. 



From the foregoing catalogue, it appears that the total number of de- 

 termined species, from rocks of the period under consideration, is, at 

 present, 416. These are distributed in groups as follows : 



Plants, - - - 9 Porcellia, - - - 4 



Corals (Polypi), - 13 Gasteropoda, - - 48 



Crinoidea, &c., - - 27 Ceiilialopoda, - - 40 



Fenestella, - - 1 Trilobites, - - 9 



Brachiopoda, - - 134 Ostracoids, - - 1 



Lamellibranchiata, - 110 Fishes, . _ _ 4 



Bellerophon, - - 13 Pleurodictyum, - - 1 



Total, _ . - _ . 410 



The number of species known, but not identified, is 20. 

 The identified species have been collected in eleven detached districts 

 or States, which have yielded, severally, the following numbers : 



1. Northern Michigan 23 



3. Southern Michigan 93 



3. Ohio 139 



4. Indiana 45 



5. Illinois 37 



6. Iowa 100 



7. Missouri : 77 



8. Kentucky 2 



9. Tennessee 13 



10. New York 9 



11. Pennsylvania 9 



Total identifications 597 



From this it appears there have been 181 identifications of species in 

 two or more of the above regicms. A furtlier analysis of the geographi- 

 cal distribution of these species will set in a strong light the palaeonto- 

 logical affinities of the several regions. 



It might be admitted at once that the outcrop at Pt. aux Barques 

 ("Northern Michigan ") is of the same geological age as the typical for- 

 mation in Southern Michigan ; but as Messrs. Houghton and Hubbard "^ 

 have separated the two series of outcrops as different formations, I de- 

 sire to introduce the palaeontological discussion, by setting at rest all con- 

 troversy respecting the synchronism of the strata in the two Michigan 

 districts. The following species occur in botli regions : 



Producta concentrica, Ctenodonta sectoralis, 



Rhynchonella Hubbardi, ' ' Stella, 



Mytilus Whitfieldanus, Goniatites Marshallensis. 



Sanguinolites borealis, 

 With 30 per cent, of the known species of the Pt. aux Barques sand- 

 stones identifiable with fossils from the Marshall sandstones, and with a 



"5 See Part I. of this paper, p. 59. 



