26 Natural History Bulletin. 



ing a number of species, was opened near Atalissa, and at the 

 same time another quarry was worked two or three miles 

 away, near the Cedar river, and at a point many feet lower 

 than the first. In the Atalissa quarry S^irifera -parryana and 

 its associated species were unusually abundant; the Cedar 

 river quarry was in the platform marked by the presence of 

 ^S". -pcnnata and its associates. 



At Buffalo in Scott count}', and at Pine Creek IVIills, Han- 

 son's quarry, Atalissa and other points in Muscatine county 

 where Spirifera -parryana occurs in the shaly limestone, it 

 has as its associates Spirifera aspera, Hall, Cyrtina nnihonata. 

 Hall, Athyris vittata, Hall, Atrypa reticularis, Linnasus, a 

 small Strophodonta and a Terebratiila of somewhat variable 

 form which I have regarded as an unusually large variety of 

 Terebratiila (^Cryptonella) linckalcBni, Hall. Th^t Atrypa re- 

 ticularis, that is found in this association is always a small 

 globose variety, rather coarsely striated, with ventral valve 

 flat or concave, and dorsal valve verv convex. This form of 

 Atrypa is never, so far as I have seen, found in the same beds 

 with S. pennata, nor can any of the other species mentioned 

 be said properly to occur on the S. pcnnata platform. An 

 apparent exception may be made with respect to a few 

 straggling specimens of Athyris vittata met with occasionally 

 in company with S. pcnnata in the limestones at Independence, 

 Iowa; but they are curiosities in collections from that locality, 

 or from any other affording species from equivalent strata. 

 On the other hand, how^ever, A. vittata is the most abundant 

 .species at Atalissa, Pine Creek and related localities; its 

 broken, crowded and cemented shells furnishing the entire 

 material for layers of considerable thickness. 



Atrypa aspera var. occidcntalis that is so common at Inde- 

 pendence and other localities furnishing S. pcnnata, is never 

 found with S. parryana, nor are any of the varieties of 

 spiniferous atrypas ever associated with it. 



Hall (Geology of Iowa, Vol. I, part 2, page 508-9,) de- 

 scribes Spirifera aspera and credits it positively to Indepen- 



