50 IOWA GEOLOGICAL SURVEY 



pustulosus , and fragments of heavy, coarsely tuberculated 

 plates indistinguishable from those of Aspidichthys. A con- 

 siderable quantity of this class of remains was brought together 

 some years ago by Mr. Clement L. Webster, of Charles City, 

 Iowa. 



State Quarry substage. — A small outlier of Upper Devonian 

 rocks near North Liberty, Johnson county, several miles north 

 of Iowa City, which has received the name of State Quarry lime- 

 stone, is remarkable for carrying a vast quantity of fish teeth, 

 a fact first discovered and made known by Professor Calvin * 

 about a dozen years ago. The remains occur in a single cherty 

 layer not over eighteen inches thick, but so great is their pro- 

 fusion as to justify the appellation given to it by its discoverer 

 as a "fish-tooth conglomerate". The homotaxial relations and 

 peculiar faunal characters of these beds have been set forth with 

 considerable fulness by Professor Calvin in his report on the 

 Geology of Johnson county, to which is appended a special 

 notice of the fish-remains by the present writer. Detailed de- 

 scriptions of the known species are also given in a subsequent 

 part of this Eeport. 



Sweetland Creek substage. — The beds that have been desig- 

 nated by this name consist of argillaceous shales that are fre- 

 quently found overlying the Cedar Valley limestone in Scott 

 county, and are not only uncomf ormable with the latter, but con- 

 tain a markedly different fauna. A description of the local 

 sections and lists of fossil species that have been found are 

 given by Professor J. A. Udden in Vol. IX (1899) of the present 

 series of Reports. Tritors of Pti/ctodus calceolus and dental 

 plates of the Synthetodus type are the only known vertebrate 

 forms in the assemblage. 



*Proc. Iowa Acad. Sci. (1896), 4, pp. 16-21. Ann. Rept. Iowa Geol. Surv. 

 (1897), VII, pp. 74, 108. 



