364 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



Dicellocepfialus Owen, Berkey, 1898, American Geol., Vol. 21, p. 290. (Dis- 

 cusses forms related to D. misa Hall.) 



Generic description. — General form, a broad ellipse, moderately 

 convex with pleural lobes more or less flattened, cephalon transverse ; 

 genal angles extended into spine : cranidium roughly subquadrangu- 

 lar in outline, with narrow fixed cheeks and strong palpebral lobes 

 posterior to the rounded outer rim of the palpebral lobes extending 

 • across the fixed cheeks as narrow ocular ridges. Glabella subquad- 

 rangular in outline, and narrowing slightly towards its broadly 

 rounded front ; posterior furrow strong and extending across the 

 glabella ; second furrow indicated by a pair of short side furrows ; a 

 third furrow is indicated ; strong flattened occipital ring. 



Facial sutures as shown by figures i, 2, and 5, plate 61. 



Thorax with probably twelve segments as in the closely related 

 genus Saukia (pi. 65). Axial lobe convex; pleural lobes depressed 

 and with each segment having a narrow, oblique furrow that begins 

 near the inner anterior margin and terminates well out and near the 

 posterior margin of the backward curving more or less bluntly pointed 

 extremity. 



Pygidium transverse, large and with a strong central axis that ter- 

 minates within a broad flattened border: it is marked by clearly 

 defined transverse rings that extend out as the pleural lobes and 

 broad border. The margin may or may not have two short postero- 

 lateral spines. 



Surface with fine irregular more or less inosculating lines and, on 

 some species, small granules over the glabella and median axis of the 

 thorax and pygidium. It is punctate in D. hartti and D. texanus, the 

 only two species in which the structure of the test is preserved. 



Some of the species of Dikelocephalus attain a large size. Speci- 

 mens of the cephalon of D. minnesotensis in the collection of the 

 United States National Museum have a length of 9 cm. and a width 

 of 24 cm. Pygidia occur 9.5 cm. in length, 18 cm. in width, and a 

 thoracic segment has a length of 16 cm. Dikelocephalus vanhornei 

 (pi. 62) is also a large species. 



Genotype. — Dikelocephalus minnesotensis Owen, 1852, 



Stratigraphic range. — Upper beds of Upper Cambrian. 



Geographic distribution. — Upper Mississippi Valley in western 

 Wisconsin and eastern Minnesota, also in central Texas, Nevada and 

 Montana. About the Adirondack Mountains of New York, in Sara- 

 toga and Franklin Counties and in central British Columbia. There 

 are many references in literature to the occurrence of Dikelocephalus 

 in various parts of America and in foreign countries, but with the 



