NO. 13 DIKELOCEPHALUS AND OTHER GENERA 377 



transverse furrow that serves to outline a narrow flattened border- 

 ing rim. The associated pygidium has a longer axial lobe. 



The specimens are all ^ from locality 20b, Upper Cambrian ; about 

 I mile (1.6 km.) above Monte Cristo Mine, Quandary Peak, Sum- 

 mit County, Colorado (Whitman Cross, collector, 1880). 



This is a large species and it may be the largest one of the genus. 

 It is also of special interest owing to its geographic position. A 

 careful search in the Upper Cambrian of the Leadville region may 

 result in finding good specimens of this species and, of still greater 

 importance, the fauna that accompanied the invasion of the Upper 

 Cambrian sea in this region. 



Formation and locality. — Upper Cambrian: (20b) about i mile 

 (1.6 km.) above Monte Cristo Mine, Quandary Peak, Summit 

 County, Colorado (Whitman Cross, collector, 1880). 



SAUKIA CRASSIMARGINATA (Whitfield) 



Plate 61, fig. 8; plate 65, figs. 9, 10; plate 66, figs. 2-5, 5a 



Dikelocephalus {minnesotensis ?) Owen, 1852 (in part), Rept. Geol. Survey 



Wis., Iowa, and Minn., p. 574, Tab. i. fig. 10. (Figure of cranidium 



doubtfully referred to D. minnesotensis.) 

 Dikelocephalus minnesotensis var. Hall, 1863 (in part), Sixteenth Ann. 



Rept. New York State Cab. Nat. Hist., p. 141, pi. 9, fig. 11 ; pi. 10, fig. 9; 



pi. II, fig. 2. (Two cranidia described and illustrated. Free cheek ten- 

 tatively referred to D. pepinensis.) 

 Dikelocephalus viinnesotensis var. H.'\ll, 1867, Trans. Albany Inst., Vol. 5, 



pi. 4, fig. II ; pi. S, fig. 9. (Reprint of figures of 1863.) 

 Dikellocephaliis crassiniarginatus Whitfield, 1882^ Geol. Wisconsin, Vol. 4, 



p. 344, pi. 27, fig. 14. (Describes and illustrates free cheek as type of 



species.) 

 Dicellocephalus Chamberlin, 1883, Geol. Wisconsin (Survey of 1873- 



1879), Vol. I, p. 129, text fig. 15. (Illustrates a nearly entire specimen 



from Prairie du Sac that is evidently this species.) 



This fine species is generically related to Saiikia lodensis (pi. 65. 

 fig. i). It differs specifically from it in having a broader border to 

 the cephalon and pygidium, broader fixed cheeks, and smooth surface 

 over the entire dorsal test. It also attains a larger size. 



An entire specimen in the collection of the United States National 

 Museum has a length of 9.7 cm., with a width of 6.8 cm. at the back 

 of the cephalon. Other proportions are shown by figure 2, plate 66. 



Several pygidia (pi. 65, fig. 9) resembling the pygidium of this spe- 

 cies occur in the coarser Jordan? sandstone (81, 8ib) near Devils 

 Lake. The specific identification must remain doubtful until speci- 



^ See also page 378, second species under Sattkia fallax. 



