THE MISSISSIPPI VALLEY EQUIVALENTS. 343 



Cincinnati group, under the name of Maquoketa shale. The formation is 

 referred without reserve to the same geological series as the rocks at Cincin- 

 nati, Ohio. The author considered the section as a local or partial develop- 

 ment of the Cincinnati series, and on that account proposed the name of 

 Maquoketa. He was also influenced by the decision of Messrs. Meek ami 

 Worthen, who held that the Hudson River groups in Indiana, Ohio, Illi- 

 nois, etc., were not equivalent to those of the Hudson series to which the 

 name of Hudson River shales was first applied. A number of species oi 

 fossils were found that are also common to the Cincinnati formation. 



In Professor S. Calvin's description of a deep well drilled at Washington, 

 Iowa,* it is stated that at 702 feet a fine bluish or greenish shale, identical 

 in all respects with the shales of the Hudson River group as seen in the 

 gulch at and below Bellevue, Iowa, continues down to the depth of 793 feet, 

 giving a thickness of 91 feet. This group of shales is plainly referable to 

 the Hudson River shales of Hall or to the Maquoketa shales of White. In 

 some " Notes on the Geology of Southeastern Iowa," C H. Gordon | 

 describes the strata passed through by a deep well at Keokuk. In this 

 section the Maquoketa shale has a thickness of 63 feet. 



During the field season of 1889, a collection of fossils was made from the 

 typical Maquoketa locality by Professor Joseph F. James, of the U. S. Geo- 

 logical Survey. Of 41 spsciesj collected aud identified, all but seven are 

 identical with those found in the fauna at Cincinnati. Stratigraphicallv, 

 the Maquoketa shale is a diminished representative of the section at Cincin- 

 nati, and it is also identical in its lithologic and paleontologic characters. 



* Notes on the formations passed through in the boring of the deep well at Washington, Iowa : 

 Am. Geol., vol. 1, 1888, p. 29. 

 f Am. Geol., vol. 4, 1889, p. 237. 



i Montindipora gracilis. Orthis < maa rata. 

 " lens. " fissicosta. 



" quadrata. " 'occidentalis. 



Streptelasma eormeulum. " testudin 



Diployraptus amplexicaule. Zygospira modesta. 



'" putillus. I' 1, rinea demi 



Heterocrinus kcterodact>ihi<. Cleidophorus negleetus. 



Poroerinus crassus. 'I) llinomya obliqua. 



IAchenocrinus erateriformis. Nucula fecunda. 



Fenestella, sp. Eyolithei parviuscu 

 Paleschni'i maculata. leolus (.'), sp. 



Lingulella eineinnatiensis. 



Lin'gula coburgensi RaphUtoma micula (subtili triata). 



daphne. Ti ntacu ' 



" modesta. Murehisonia gracil 

 " pro-' 



" a- hit fieldi. Pleurotom rata. 



,,,,, r,7 osa . Orthoeeras son 



Trematis, sp. Plumulites /"//".v. 



Leptaena serieea. Beyrichia, sp 



Strophomi na alternata. Aeidaspia crosoiu 



rhomboidalis.vsLr tenui triata. Calyinene callicephala. 



Orth;.< biforata. ' ' '"'"• 



XLV— Bun.. Geol. Soc. Am., Vol. 1, 1889. 



