492 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



No one familiar with the passage beds between the Devonian and 

 and the Carboniferous would hesitate to refer even the basal portion of the 

 Madison limestone to the latter. Yet the fauna of the Madison, and espe- 

 cially, perhaps, that of the lower portion, is not without Devonian affinities. 

 These are vested chiefly in the genera Productella, Aulopora, and Mich- 

 elinia, and in the species Camarotcechia sappho (?) and Spirifer subattenuatus. 

 Productella alifera n. sp., it will be noticed, is confined to the lower portion 

 of the formation, but P. cooper ensis, a highly characteristic Kinderhook species, 

 beginning in the lowest bed of the Madison limestone, survives almost to its 

 upper limit. Aulopora geometrica n. sp. is found at only one locality in our 

 collections, which occurs a little below the middle of the formation (bed 26). 

 Michelinia seems to be restricted in its occurrence to the lowest bed. 

 Camarotcechia sappho (?) also is found toward the base, in bed 25, while S. 

 subattenuatus has not been located in any bed of the section scheme. 



As is well known, C. sappho and Sp. subattenuatus occur in both 

 Devonian and Carboniferous deposits. 



The following conclusions have been drawn from the evidence afforded 

 by the table of distribution of species given on page 484, some of which 

 has already been dwelt upon: (1) The fauna of the Madison limestone 

 can be referred wholly and without question to Carboniferous time; (2) it 

 has a marked Kinderhook facies; (3) it is essentially the same fauna as 

 that described by White, by Hall and Whitfield, and by Meek, and by 

 them referred to the Kinderhook or Waverly; (4) the fauna is not sep- 

 arable into independent units, but must be regarded as a whole. 



The last statement should perhaps be qualified to some extent, for while 

 a large percentage of types, often primitive and indicating a Kinderhook 

 fauna, are persistent almost to the very top, at the same time there are 

 unquestionable indications of advancing development, while certain admix- 

 tures, sometimes specific, sometimes generic, indicate an age much later than 

 the Kinderhook. For instance, the only representatives of the Devonian 

 genera Aulopora and Michelinia are confined to the lower portion of the 

 Madison, as are also the species Leptcena rhomboidalis, Productella alifera n. 

 sp., Camarotcechia sappho (?), and Syringothyris carteri, while Endothyra baileyi 

 var. parva n. var., Derbya keokuk (?), Archimedes sp., and Seminida madison- 

 ensis n. sp. (of the type of S. subquadrata and S. subtilita) are peculiar to the 

 upper portion. At the same time it will not be amiss to recall again that 45 



