DESCRIPTION AND ENUMERATION OF SPECIES OF THE 

 AMERICAN DAKOTA GROUP FORMATION. 



I. CRYPTOa^M^E. 

 THALLOPHTTES. 



ZONASITES, Brgt. 



Zonarites digitatus, Gein. 

 " U. 8. Geol. Rep." v\, p. 44, pi. i, fig. 1. 



The relation of this vegetable organism to that described by Brong- 

 mart and Geinitz is contested on account of the habitat in a different 

 Geological stage, Geinitz having described his plant from the Dyas. As 

 species of Thallophytes of the Devonian are represented by identical 

 forms in more recent formations, even in the Cretaceous of Europe, the 

 objection is not imperative. 



ACROGENS. 



EQUISETACE^. 



EaUISETUM, Linn. 



Equisetum nodosum, sp. nov. 



Stems small, one-half to one centimeter in diameter, obscurely narrowly striate; 

 articulations very inflated, marked with broad round scars of points of attachment of 

 branches above the line of division. 



The species is distantly related to U. amissum, Heer, "FI. Arct.,'" Ill, 

 p. 60, pi. xiii, figs. 2-8, of the Lower Cretaceous of Kome, essentially 

 differing by the inflated articulations. It is represented by specimens 

 Nos. 473, 536 of the Museum of Comp. Zool., Cambridge; they are too small 

 and obscure for definite comparison. 



Hab.—'l miles N. E. of Glasco, Kansas ; collected by Chs. Sternberg. 



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