PROCEEDINGS OF THE ACADEMY OF 



Descriptions of FOSSILS from the Yellow Sandstones lying beneath the 

 " Burlington Limestone,'' at Burlington, Iowa. 



BY ALEXANDER WINCHELL. 



With the view of collecting facts bearing upon the determination of the 

 geological age and equivalents of certain ferruginous sandstones in the lower 

 peninsula of Michigan, which I have provisionally designated the Marshall 

 Group,* I visited several of the neighboring States during the past summer, 

 for the purpose of examining the principal exposures of strata supposed to 

 occupy nearly the same horizon. At Burlington, Mr. C. A. White accompanied 

 me in all my examinations, and enabled me to procure nearly a complete suite 

 of the species of that place described by Shumard and Hall, but more espe- 

 cially by himself and Mr. R. P. Whitefield.f Besides the recognized species, 

 I obtained from Mr. White, or by his assistance, several undescribed forms. 

 Subsequently Mr. White greatly increased the number of unknown species by his 

 discoveries at exposures hitherto but little explored. The whole collection of 

 new species, together with his own observations thereon, has been kindly 

 placed in my hands for investigation ; and the following paper is the result of 

 this study. 



The number of new species herein described is fifty-niae, and the number now 

 first identified, ten. The number of species previously known from these rocks 

 was sixty-six, J a total which is now raised to one hundred and thirty-five. 



The richness of this locality in fossil species is well worthy of note. To 

 the one hundred and thirty-five species from the yellow sandstones must 

 be added three hundred and seven species from the overlying Burlington lime- 

 stone, making a grand total of four hundred and forty-two species from a single 

 locality. It ought not to be forgotten, that this wonderful result has been 

 developed mainly through the industry and skill of a single individual, 

 Charles A. White, who, during eight years of his residence in the locality, 

 has collected the types of two hundred new species and six new genera. 



A consideration of the general conclusions deducible from the study of the 

 palaeontology of the rocks of the Western States supposed to occupy the 

 horizon of the Marshall Group of Michigan will be hereafter presented. Suf- 

 fice it to say, on the present occasion, that no one can glance over the list of 

 species described here and elsewhere from these rocks without admitting that 

 the ensemble bears a very close analogy with that of the " Mountain Limestone" 

 of the Old World, and raising the inquiry how the equivalent of the old red 

 sandstone can lie on the top of such an assemblage of strata. 



Descriptions of New Species and Genera. 

 LEPTOPORA, n. gen. 



Etymology, As/ttcc, shallow andirs/a, a cell. 



Corallum occurring in thin discoidal masses; cells very shallow, crowded, 

 polygonal, separated by a common cell-wall, which is vertically striated ; 

 interior of cells filled with a finely vesicular tissue; cups polygonal, con- 

 cave, elevated in the centre, and displaying numerous radial lamellae. 



* See " First Biennial Report" of the Geological Survey of Michigan, 1860. For descriptions of 

 the fossils of this group, see Silliman's Journal, [2,] vol. xxxiii. p. 3D2, and Proc. Acad. Nat. Sci. 

 Fhila., Sept., 1S62, p. 405430. , ,. 



t For White's descriptions, see Jour. Bos. Soc. Nat. Hist., vol. vn., and Proceedings of same, 

 vol. ix. p. 28, et sea- For White and Whitefield's descriptions, see "Proceedings, vol. vm. 



tin this estimate I omit Chonetes Lngani, Norwood and Pratten, (not Hall,) Cardiomorpha 

 av.tia, Hall, and Cardiomorpha parvirostris, White, for reasons whirh will appear in the sequel. 

 Product us Shumardianus, Hall, as recognized at Burlington, appears to be P. concentricus. Hall. 

 and Avicula circulus, Shumard, as recognized at Burlington, is probably Aviculopectcn limeejormis. 

 White and Whitefield. _ T 



[Jan. 



