Geology and Natural History. 151 



limited to the state quarry stage. The great mass of cemented 

 crinoidal debris comprising the beds in Graham township and the 

 upper ten or fifteen feet of the formation at the state quarries, 

 has no parallel in any other stage of the Iowa Devonian. The 

 presence of Dipterus, which elsewhere occurs only in the upper 

 Devonian, tends likewise to separate this from the underlying 

 Cedar Valley formation. In this connection it may be noted that 

 the Rhynchonelloid shell Pugnax pugnus is a Carboniferous 

 rather than a Devonian type. It is true that this species is found 

 in the upper Devonian of New York, and at the same horizon in 

 Europe ; but it is in the Carboniferous, particularly in Europe, 

 that it attains its fullest development. Faunally, therefore, the 

 relations of the state quarry limestone are with the upper, and 

 not with the middle Devonian, as is the case with the Cedar 

 Valley beds; and so all the phenomena relating to this limestone 

 and its interesting fauna seem to require for their interpretation 

 a number of crustal movements and a period of erosion in the 

 Iowa Devonian heretofore unsuspected." 



To the reviewer of this report the phenomena of this quarry are 

 recognized as a confirmation of the theory advanced several years 

 ago* that the Cuboides fauna of the Tully limestone in New York, 

 when studied in comparison with the faunas occurring below it in 

 the New York series of Devonian, must have had an origin from 

 the west and north, by the migration of faunas, rather than in 

 any modification of launas existing in the immediate region pre- 

 vious to the time of the Tully limestone. 



The writer has for several years been expecting to find evidence 

 of a barrier having existed in early Devonian time, extending lrom 

 the Archaean tongue of Wisconsin toward the ancient island of 

 southeastern Missouri. According to my interpretation of the 

 several Devonian faunas of America, a continuity of the faunas, 

 after the Cuboides zone appeared in the New York area, is noticed 

 in the whole extent of the northern Devonian from New York to 

 Iowa, through the Mackenzie river, across to China and on to the 

 European formations as far as Devonshire in England. 



This continuity of faunas does not appear in the Middle Devo- 

 nian formations, but the brake seems to separate the well known 

 New York faunas from those of Iowa and the Mackenzie valley, 

 and Nevada. The barrier, therefore, was supposed to exist some- 

 where between Iowa and New York. The State Quarry limestone 

 of Iowa has furnished Prof. Calvin with the very evidenee I have 

 been looking for. This evidence points to the occurrence of vio- 

 lent disturbance of the preexisting quiet sea, the removal in places 

 of channels through the deposits, the sudden local and wholesale 

 destruction of life — with the introduction of a fauna new to that 

 region, but which, like the Cuboides fauna proper, is characteris- 

 tic of the stages following, and not preceding the Cuboides zone 

 in* the Noith American region. h. s. w. 



* The Cuboides zone and its fauna, Bull. Geol. Soc. Am., vol. i, pp. 481-500, 

 1890. 



