476 



GEOLOGY. 



and Mackenzie valley (Fig. 212, r and s). These strikingly illustrate 

 the community of this wide-ranging fauna, and its close approach 

 to a cosmopolitan fauna. Now none of these species had any repre- 

 sentative at all closely allied to it in the southern Hamilton, nor are 

 there any species in it from which these forms could probably have 

 been derived. On the other hand, allied forms have been found in 

 England, Belgium, France, Germany, Russia, Persia, and China. This 

 seems to make it clear that the derivation was from that quarter, 

 and that, while the American northwestern fauna had close connection 



Fig. 212. — Upper Devonian Brachiopoda, showing the geographic distribution of 

 five species: Spirifer disjunctus Sow.; a, England; b, China; c, Mackenzie valley; 

 d, New York. Hypothyris cuboides (Sow.); e, New York; /, Russia; g, China; 

 h, England; i, Great Basin. Schizophoria striatula (SchL); j, Mackenzie valley; 

 k, New York; I, England; m, China; n, Iowa; o, Nevada. Gypidula comis (Owen); 

 p, Iowa; q, China. Spirifer tullius Hall; r, New York; s, Mackenzie valley. 



with the Eurasian continent, it had no previous migratory relations 

 with the eastern and southern Hamilton province. This is further 

 strengthened by the fact that while the latter had species of South 

 American origin, none of these latter are found in the northwestern 

 fauna previous to the joining of the two provinces at the close of this 

 stage. Wide-ranging as both the Hamilton faunas were, they had 

 not yet entirely escaped from provincial limitations. 



The corals of the northwestern Hamilton fauna were of the Onon- 

 daga type, which seems to indicate that at an earlier stage the Onon- 

 daga fauna and the ancestors of the northwestern Hamilton fauna 

 came into communication, as might well have happened from the 



