NO. 13 DIKELOCEPHALUS AND OTHER GENERA 369 



and Cooper Curtice, 1883) ; also (m), at the top of the Potsdam 

 sandstone on Marble River, i mile (1.6 km.) south of Chateaugay, 

 Franklin County (C. D. Walcott, 1886), all in New York. 



DIKELOCEPHALUS ? LIMBATUS Hall 



Plate 65, figs. 5-8 



Dikelocephalus tiiinnesotensis var. liiiibatus Hall, 1863, Sixteenth Ann. Rept. 

 New York State Cab. Nat. Hist., p. 141, pi. 9, fig. 12. (Describes and 

 illustrates anterior portion of a cranidium.) 



Diccllocephalus minnesoteiisis Owen, WI^XHF.LL, 1864, American Journ. Sci., 

 2d ser.. Vol. S7' P- 229. (Remarks on occurrence of a species of Diccllo- 

 cephalus doubtfully referred to this species.) 



Dikelocephalus vii)uiesotciisis var. limbatus Hall, 1867, Trans. Albany 

 Inst., Vol. 5, p. 121, pi. 4, fig. 12. (Reprint of paper of 1863.) 



This very interesting species is represented by several fragments 

 from locality 78 where the cranidium represented by figure 6 is asso- 

 ciated with the pygidium represented by figure 7. The broad, slightly 

 concave, frontal limb and subquadrilateral glabella bring the species 

 close to Dikelocephalus as does the associated pygidivun. The latter 

 has the relatively short axial lobe and broad flattened border of the 

 pygidia of D. minnesotensis, but it dififers in the details of the furrows 

 on the pleural lobes and in the absence of spines on the margin. 



Dr. James Hall considered the fragment that he described as a 

 variety of D. minnesotensis^ but with the specimens now available for 

 study the varietal name limhatus is used as the specific name. 



Formation and locality. — Upper Cambrian : St. Lawrence forma- 

 tion; (78) quarry near St. Croix River, in suburbs of Osceola, Polk 

 County (L. C. Wooster, 1883) ; (78b) 50 feet (15.2 m.) above St. 

 Croix River, near the landing at Osceola, Polk County (Cooper 

 Curtice, 1884), and (134a) in a quarry i mile (1.6 km.) southeast 

 of the county court house, in Menomonie, Dunn County (Chas. 

 Schuchert, 1893), all in Wisconsin. 



A number of specimens of the pygidium and free cheeks of a 

 species closely related to D. ? limbatus occur in the Jordan sandstone 

 (8ib), near Devils Lake, Sauk County (Cooper Curtice, 1884). 

 These are the forms described by Dr. Alexander Winchell. One 

 of the pygidia is illustrated by figure 8, plate 65. 



DIKELOCEPHALUS MINNESOTENSIS Owen 



Plate 60, figs. 1-8; plate 61, figs. 1-3, 5-7; plate 62, figs. 4-6; plate 66, fig. i. 



Asaphus Owen, 1848, Rept. Geol. Reconnaissance, Chippewa Land District, 

 Senate Doc, Exec. No. 57, 30th Congress, p. 15, pi. 7, figs. 2, 3. (Illus- 

 trates cranidium and pygidium under name Asaphus.) 



