426 Williams — Fossil Faunas and their use in 



The first ten species of this list exhibit, by the method used 

 in measuring them, a bionie value of 33 per cent and over in 

 the fauna to which they belong, and, therefore, they may be 

 regarded as the characteristic species of the fauna for the 

 region examined. They maintain their position of bionie 

 dominance, geographically, over the eastern half of New York 

 and down into Pennsylvania; and geologically, throughout 

 over a thousand feet of thickness of sediments called the 

 Hamilton formation. 



The introduction of evidence from other faunules of the 

 same region slightly modifies the percentages, but the differ- 

 ences are not greater than might be expected from the imper- 

 fection of the statistics themselves. 



For instance, I have examined another group of 37 faunules 

 from the Unadilla region, recorded by Prosser.* In a list of 

 the ten species with highest bionie index, are eight of the 

 standard list. If they are incorporated with the eastern fau- 

 nules already tabulated, the result is the same for the first twelve 

 of the resulting list, based upon the total (146 + 37 =) 183 

 faunules. 



The Hamilton species from Ontario, Canada, given by 

 Whiteaves in his revised listf includes eight of the twelve 

 dominant species of our list, but the facts of abundance, rarity, 

 or frequency are not noted by Whiteaves, hence the actual 

 bionie relations of the species cannot be stated. 



Among the few species recorded by Pominger^: as occurring 

 in the Michigan area are named five of the standard list. 



In the list of species from Milwaukee, recorded by Teller 

 & Monroe,§ are named four of the standard ten. 



In Mr. Weller's list of species for southern Illinois | are 

 mentioned three of the standard ten species. 



In Indiana, Dr. Kindle^ has recorded from the Sellersburg 

 faunule three of the standard list. 



The Iowa Devonian lists show only a single species of the 

 standard dominant species of the fauna (viz : Phacops ra?ia), 

 and the Devonian of Manitoba, Saskatchewan and McKenzie 

 Piver regions, which has been studied by Dr. Whiteaves, - ** 

 shows not a single species of the typical list. 



* The Devonian section of central New York along the Unadilla River. 

 46th Ann. Kept., N. Y. State Museum, pp. 256-288, 1893. 



f Revised list of the fossils of the Hamilton formation of Ontario, Geol. 

 Surv. Canada, Contrib. Can. Paleontology, vol. i, p. 412, 1898. 



X Geol. Surv. Michigan, vol. iii, pp. 38 and 63. 1873-1876. 



§ Jour. Geol., vol. vii, pp. 272-283, 1899. 



1 Jour. Geol., voJ. v, pp. 625-635, 1897. 



^[25th Ann. Rept. Dept. Geol., etc., Indiana, pp. 530-775. 



** Geol. Surv. Canada ; Contr. Canadian Paleontology, vol. i, pts. iii and iv, 

 1891 and 1892. 



