74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



Formation and locality. — Upper Cambrian: (66) Hamburg lime- 

 stone? On first ridge north of the Dimderberg Mine, Eureka District, 

 JSTevada, 



Subfamily DIKELOCEPHALIN^ Beecher 



Dikelocephalinse Beecher, 1897, Amer. Journ. Sci., 4th Ser., Vol. 3, p. 192. 

 In a paper on Dikelocephalus and other genera of the Dikelo- 

 cephalinse ^ I included in this subfamily : 



Dikelocephalus Owen 1852. 

 Conokephalina Brogger 1886. 

 Calvinella Walcott 1914. 

 Osceolia Walcott 1914. 

 Saiikia Walcott 1914. 



To the above five genera there is nov^ added Briscoia Walcott which 

 occurs in the lower beds of the Mons formation of the Ozarkian of 

 Alberta and British Columbia, and the Lower Ozarkian of Devils 

 Lake and Mendota formations of Wisconsin and Hoyt limestone of 

 New York. The non-spinose species belonging in the Upper Cam- 

 brian are also included. 



BRISCOIA Walcott 



Briscoia Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. i, p. 2)7- 



Briscoia is founded on the cranidium, free cheeks, fragments of 

 thoracic segments and entire pygidia of a large trilobite that occurs 

 in the lower portion of the Mons formation. 



Observations. — Briscoia differs from Dikelocephalus in its elongate 

 glabella, frontal limb and course of the facial sutures in front of the 

 glabella, and in the latter the suture is intramarginal to the center 

 while in Briscoia the suture appears to be intramarginal for a less 

 distance : the most strongly marked difference, however, is the 

 presence of the characteristic postero-lateral spine on the pygidium 

 of Dikelocephalus. The thoracic segments are essentially the same. 



Genotype. — Briscoia sinclairensis Walcott. 



Stratigraphic range. — Ozarkian, lower portion of the Mons for- 

 mation. Hoyt limestone of New York. Upper Cambrian of Wis- 

 consin and Minnesota. 



Geographic distribution. — Cordilleran area of Alberta and British 

 Columbia, from Glacier Lake to Mount Sabine at the southern end 

 of the Stanford Range; Saratoga County, New York; Devils Lake 

 sandstone and Mendota limestone areas of Wisconsin. 



^ Smithsonian Misc. Coll., 1914, Vol. 57, No. 13. 



