Contributions to Paleontology. 



151 



The proportions continue very nearly in all the parts except the frontal 

 limb, which, in the larger one, has but twice the length of the smaller one, 

 while the other parts are about three times as great. Since we find similar 

 fragments of thoracic segments, and portions of the pygidia associated in 

 the same specimens with the glabella, I can have no doubt of their identity 

 with C. iowensis. 



The illustrations on Plate iii, f. 10 - 12, are from Trempaleau, 

 and are of the largest individuals found there. Subsequently Dr. 

 Shumard has sent to me specimens of the glabella and fixed cheeks 

 of several individuals from Black river, which are much larger. 

 These are illustrated on Plate ii, f. 30. 



At the mouth of Root river this species occurs of much larger 

 dimensions than the specimens of Trempaleau, and considerably 

 larger than those from the Black-river locality. The Root-river 

 beds are apparently somewhat higher in the series than those of 

 Trempaleau or Mountain island; but beyond this and one other 

 species, I have not identified fossils from that locality. 



The C. iowensis is a well-marked and very characteristic specie3 

 of the lower fossiliferous beds of the Potsdam sandstone. 



Dr. Shumard remarks that "this species may be readily dis- 

 tinguished from the Crepicephalus [ Conocephalites ] vnsconsensis, 

 Owen, to which it is somewhat nearly allied, by its wider and more 

 conical glabella, and much narrower front margin." 



This fossil occurs with Conocephalites minor, Lingula, Obolella? 

 and Theca, at Trempaleau; and in a similar association, near the 

 mouth of Black river in Wisconsin. The larger specimens, from 

 Root river, are associated with fragments of Trilobites, among which 

 no other fossils have been observed. 



CONOCEPHALITES WISCONSENSIS. 



PLATE II, FIGS. 39-41 ; AND PLATE III, FIGS. 22, 23, 24, 27 & 28. 



Crepicephalus ? wisconsensis : Owen, Geological Report of Wisconsin, Iowa 

 and Minnesota, Tab. 1, f. 13. ( The upper figure on the speci- 

 men, the lower figure being Dikelocephalus granulosus.} 



Compare Dikelocephalus latifrons : Shumard, Trans. Acad. Sciences of St. 



Louis, Vol. ii, p. 101. 



Head large. Glabella strong, truncate-conical, mode- 

 rately convex, sometimes subangular in the middle, 

 width at base nearly equal to the length ; front usually 



