OBOLID^. 399 



Gordon and Youngs creeks, about halfway between Gordon Mountain and Cardinal Peak, Oyando quadrangle (U. S. 

 Geol. Survey), Powell County, Montana. 



(15p) Limestones near the north end of the Fish Spring Range, Tooele County; and (15x) limestones near the 

 middle of the Fish Spring Range, near the hue between Juab and Tooele counties; both in Utah. 



(lln) About 3,000 feet (914.4 m.) above the Lower Cambrian and 1,400 feet (426.7 m.) below the Upper Cambrian 

 in the upper part of the limestone forming la of the Marjum hmestone [Walcott, 19081, p. 179], in the long cliff 2 miles 

 (3.2 km.) southeast of Marjum Pass; (llo) about 2,750 feet (838.2 m.) above the Lower Cambrian and 1,650 feet (502.9 

 m.) below the Upper Cambrian, at the base of the limestone forming la of the Marjum limestone [Walcott, 1908f, 

 p. 179], about 4 miles (6.4 km.) southeast of Antelope Springs in the spur at the junction of the Deseret and Swasey 

 Spring roads; (llq and 30g) "• about 2,350 feet {716.3 m.) above the Lower Cambrian and 2,050 feet (624-S m.) below 

 the Upper Cambrian in the limestone forTning le of the Marjum limestone [Walcott, 1908f, p. ISO], ridge east of Wheeler 

 Amphitheater; (3x and 3y) about 2,200 feet (670.6 m.) above the Lower Cambrian and 2,200 feet (670.6 m.) below 

 the Upper Cambrian in the limestones forming Id of the Marjum limestone [W'^alcott, 1908f, p. 180], ridge east of 

 Wheeler Amphitheater; (3s and 8g) about 1,700 feet (518.2 m.) above the Lower Cambrian and 2,700 feet (823 m.) 

 below the Upper Cambrian in the shaly limestones and calcareous shales of the Wheeler formation [Walcott, 1908f, 

 p. 181], in the eastern part of ^'^^leele^ Amphitheater east of Antelope Springs; (8i) shales believed to be referable 

 to the lower portion of the Marjum limestone [Walcott, 1908f, p. 180], found about 0.5 mile (0.8 km.) east of Antelope 

 Springs; and (8k) shales 0.5 mile (0.8 km.) northwest of Tyler Springs, east slope of House Range east of Antelope Springs; 

 all in the House Range [Walcott, 19081, Pis. XIII and XV], Millard County, Utah. 



(541i) About 3,140 feet (957.1 m.) above the Brigham quartzite and 1,050 feet (320 m.) below the Upper Cam- 

 brian in the Hmestones forming la of the Bloomington formation [Walcott, 19081, p. 194], in Blacksmith Fork Canyon, 

 about 9 miles (14.4 km.) east of Hyrum, Cache County, Utah. 



Middle? Cambrian: (34v) Limestone about 1,750 feet (533 m.) above the Cambrian quartzitic sandstones about 

 2 miles (3.2 km.) southeast of Muskrat Spring, on the northwest face of Grantsville Peak, Stansbury Range, Tooele 

 County, Utah. 



Obolus MjERA (Hall and Whitfield). 

 ly 



Plate X, figures 2, 2a-e. 



Lingulepis mxra Hall and Whitfield, 1877, U. S. Geol. Expl. 40th Par., vol. 4, p. 206, PI. I,- figs. 5-7. (Described 



and discussed as a new species. The specimens represented by figs. 6 and 5 are redrawn in this monograph, 



PI. X, figs. 2a and 2b, respectively.) 

 Lingulepis mxra Hall and AVhitfield, Walcott, 1884, Mon. U. S. Geol. Survey, vol. 8, pp. 12-13. (New localities 



mentioned.) 

 Lingulella f mxra (Hall and Whitfield), Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, 



p. 61. (Suggests change in generic reference.) 

 Lingulella^ mxra (Hall and Whitfield), Walcott, 1897, Am. Jour. Sci., 4th ser., vol. 3, p. 404. (Merely changes 



generic reference.) 

 Obolus (Lingulella) mxra (Hall and Whitfield), Walcott, 1899, Mon. U. S. Geol. Survey, vol. 32, pt. 2, p. 443. (Merely 



changes generic reference.) 



General form round ovate, wdth the ventral valve broadty subacummate and the dorsal 

 valve obtusely rounded; valves rather strongly convex, the convexity increasing gradually from 

 the margins to the umbonal portion of the shell, where it is greatest. Surface marked by con- 

 centric lines and fine striae of growth and very fiiie indistinct radiating striae that can be seen 

 only with a strong glass in a refiected light. When the outer layer of the shell is exfoliated the 

 surface is marked by numerous radiatmg striae, becommg coarser toward the front, where they 

 outline narrow, slightly raised ribs ; this latter feature varies from simple radiating striae to the 

 appearance of narrow ribs; the ulterior surface has not been seen. The shell is formed of a 

 rather thin outer layer and numerous inner layers, which make a strong, thick shell; the inner 

 lamellae over the anterior portions of the shell are oblique to the outer layer and when the shell 

 is partly exfoliated appear as imbricating layers. A small A^entral valve 10 mm. in length 

 has a width of 8 mm. A larger associated dorsal valve has a length of 11 mm., width of 10 mm. 



The only portion of the interior of the shell thus far discovered is an imperfect cast of a 

 portion of the area of a ventral valve (PI. X, fig. 2). 



Observations. — This species is most nearly related to 0. matinalis (Hall) (PL VIII). It 

 differs from that in being somewhat more elongate, although some examples vary but little from 

 0. Tnatinalis. The fact that it occurs in the Upper Cambrian near the base of the Ordovician 

 has more influence in leaving it as a distinct species than any differences which have been thus 

 far observed. 



a llq Is the type locality. 



