NO. 5 CAMBRIAN TRILOBITES 363 



yon, 0.25 mile (0.4 km.) below Sixteen Post Office, Meagher County, 

 Montana. 



DOLICHOMETOPUS BION, new species 



Plate 52, figs. 2, 2a-c 



Bathyuriscus product us (Hall and Whitfield) Walcott, 1908, Smithsonian 

 Misc. Coll., Vol. 53, p. 198. (Named in list of fossils found in i of 

 Spence shale.) 



This is one of the largest species of the genus. It differs from 

 D. productus (pi. 53, figs. 2, 2a-d, 3, 3a, 4, 4a) in position of the pal- 

 pebral lobes and more expanded glabella. The associated pygidium 

 has a shorter axial lobe and broader border. Outer surface of test in 

 cast nearly smooth. 



Only one cranidium has been found. This has a length of 16 mm. 

 The largest associated pygidium has a length of 32 mm. The out- 

 lines of the pygidium vary owing to impression and distortion in the 

 argillaceous shale. 



Formation and locality. — Middle Cambrian: (55c) Spence shale 

 member of the Ute formation; about 50 feet (15.2 m.) above the 

 Brigham quartzite, and 2,755 feet (839.7 m.) below the Upper Cam- 

 brian, in a ravine running up into Danish Flat from Mill Canyon, 

 about 6 miles (9.6 km.) west-southwest of Liberty and 15 miles 

 (24.2 km.) west of Montpelier, Bear Lake County, Idaho. 



DOLICHOMETOPUS BOCCAR, new species 



Plate 52, figs. I, la-f 



This interesting species at once suggests D. productus (pi. 53, figs. 

 2, 2a-d, 3, 3a, 4, 4a) . It differs in the more posterior position of the 

 palpebral lobes in relation to the length of the glabella. Compare 

 figures 3a and 4a, plate 53, with figures i and ic, plate 52. The 

 pygidia of the two species are very much alike. 



The stratigraphic horizon of the specimen of D. productus from 

 Mount Stephen, British Columbia, is in the lower portion of the 

 Ogygopsis shale ' and that of D. boccar about 200 feet below in lime- 

 stones of 2d in the Mount Bosworth section.' 



A species apparently identical with this was found in a loose block 

 of limestone on the southwest side of Moose Pass at the head of 

 Moose River in which the glabella and palpebral lobes have about 

 the same form, also the pygidium. 



Smithsonian Misc. Coll.. Vol. 53, 1908, p. 210. 

 Idem, p. 211. 



