PAPERS OX GEOGRAPHY AND GEOLOGY 245 



24. Hebertella insculpta (Hall) (c) W. 



- Hebertella occidentalis (Hall) (c) Richmond 

 Leptaena unicostata (Meek and Worthen) (c) 

 Plectambonites sericeus (Sowerby) (c) W. L. 



2>. Plectortbis whitfieldi (Winchell) near P. kankakensis (McC) 

 (c) 



29. Rafmesquina alternata (Conrad) (c) Richmond 



30. Strophomena neglecta (James) (c) W. 



31. Stromphmena planumbona (Hall) (c) W. L. 



32. Byssonychia radiata (Hall) (r) Richmond 



33. Modiolopsis concentrica (Hall and Whitf.) (r) W. 



34. Pterinea dei: nrad) (r) Richmond 

 ' 'onradella sp. 



Cyclonema sp. 

 Hormotoma sp. 

 Liospira sp. 



39. Lophcspira sp. 



40. Tentaculites sterlingensis M and W. 



In the fauna from the upper Maquoketa beds seven 

 miles west of Preston, Iowa, there are five species that 

 in Indiana are restricted to the TVaynesville formation 

 of the Richmond, and not one of the spe' Uagnos- 



tic of a higher horizon in the Indiana and Ohio Rich- 

 mond. The fauna clearly corresponds with that from 

 the upper Maquoketa east of Sterling, and with the fauna 

 listed from the localities above described in Illinois. 

 These very fossiliferons upper Maquoketa strata are 

 well exposed in the bed of a stream where it joins 

 the Mississippi River about two miles south of Bellevue, 

 in Jackson county, and at Patterson's Spring, one mile 

 north of Brainard, in Fayette county, and at several 

 other places in northeast Iowa where they contain a 

 fauna similar to that listed from seven miles west of 

 Preston. 



If this correlation is correct, the conclusion follows 

 that the uppermost fossiliferons strata of the Maquo- 

 keta in Iowa and northwest Illinois are of Fernvale age, 

 and they represent the time of Waynesville deposition 

 in Indiana and Ohio. The earlier Maquoketa strata in 

 Iowa lack many of the characteristic early Eichmond 

 species of fossils present in Indiana and Ohio, and they 

 contain a number of species that are more distinctly 

 northwest Eichmond forms such as Dicranopora fragilis, 

 Dinorthis proavita, and Leptaena unicostata, that do not 

 occur in the Indiana-Ohio basin. It is thought that the 

 sea in which the lower and middle Maquoketa strata were 

 deposited advanced from the northwest into Iowa and 



