Twenhofel and Dunbar — Nodides xoith Fishes. 161 



can. No bracbiopods appear to be present. Tbe fossils which 

 have been identified are Aviculopecten occidentqlis, Aslartella 

 sp., Edmondia cf. nebraskensis, E. sp., Macrodon tenuistria- 

 tus, M. sp., Nucula bellistriata, JV. cf. beyrichia, N. ven- 

 tricosa, Dellerophon cf. crassus, Euphemits carbonarius, 

 Tveposjpira sphcerulata, Metaeoceras sangamonense, Dhillipsia 

 major, and quite a number of additional pelecypods which 

 have not been determined. 



The underlying Kickapoo limestone contains "sixty-two 

 species, eighteen of which are bracbiopods, while no fossils 

 have been reported from the Lawrence outcrops of the over- 

 lying Lawrence shale, and, except for Prestwiehia danas, none 

 have been discovered elsewhere. In this respect they resem- 

 ble the Bandera, LeRoy (fossil insects excepted), and Tecum- 

 seh shales, while several others of the Kansas shale zones 

 contain only a few species. 



Conditions of Deposition. — The Kansas Coal Measures 

 consist of a series of alternations of more or less barren shales 

 and thin fossiliferous limestones, of which many of the latter 

 can be traced as escarpments or terraces from the northern 

 side of the state to the southern, and, in addition, several of 

 them have been traced into Nebraska, Missouri and Oklahoma. 

 The shale zones are generally not highly calcareous, and most 

 of them locally contain thin bands of coal, or highly carbona- 

 ceous shale, a thin bed of the former outcropping on the cam- 

 pus of the State University. The limestones are of marine 

 origin, and such is also true of many of the shales, but it is 

 certainly equally true that some of the latter are to be con- 

 sidered as deposits of freshwater origin. The absence of 

 thick zones of coarse sandstone permits the inference that the 

 land was not of great relief, and was probably characterized by 

 sluggish, meandering streams which spread layers of mud over 

 their flood plains and deltas. During times of relative stabil- 

 ity the delta extended into the sea, which the typical marine 

 deposits indicate w r as at no time of great depth. The shore is 

 probably to be conceived as a wide mud fiat with small shore 

 lakes and swamps, over which the tide swept for greater or 

 less distances. Intermittent submergence would from time to 

 time bring portions of the mud beneath the sea and initiate 

 the deposition of limestone, thus giving rise to an interfinger- 

 ing of marine and continental deposits — a type of sedimentary 

 structure characteristic of delta deposits which have been laid 

 down in shallow seas.* 



The Kickapoo limestone represents an incursion of the sea, 

 while the Lawrence shale indicates the possible driving back 

 * Barrell, Jour. Geol., vol. xlv, p. 354, 1906. 



