418 CAMBRIAN BRACHIOPODA. 



section, and the localities are 400 miles apart. The variety leda differs from the species in 

 having more numerous fine threadlike strise and in having the ventral valve on the average 

 more obtuse in old shells. 



Formation and locality. — ^Tipper Cambrian: (30m) About 1,950 feet (584,4 m.) above the Middle Cambrian 

 and 1,350 feet (411.5 m.) below the top of the Upper Cambrian in the siliceous limestones forming le of the Notch 

 Peak limestone [Walcott, 1908f, p. 175], on the slopes of Notch Peak, about 5 miles (8 km.) southwest of Marjum 

 Pass, House Range [Walcott, 1908f, PI. XIII], Millard- County, Utah. 



Obolus tetonensis ninus Walcott. 

 u 



Plate VIII, figures ll-o; Plate XI, figures 1, la-g. 



Obolus tetonensis ninus Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 328. (Characterized essentially asbelow as 

 a new variety.) 



This variety differs from Oholus tetonensis Walcott and from 0. matinalis (Hall) by the 

 more elongate form of the dorsal valve and the more acuminate form of the ventral valve, the 

 cardinal slopes of the latter extending much farther forward in the variety ninus than in the 

 two species. 



The advanced position of the visceral area in the ventral valve is shoMTi by Plate XI, figure 

 lb, and in the dorsal valve by Plate XI, figure Ig. The advanced position of the latter may be 

 compared with the visceral area of Oholus (Schmidtia) crassus Mickwitz. 



Formation and locality. — TTpper Cambrian: (12m) Arbuckle limestone (in the section 7 miles (11.2 km.) north 

 of Springer this horizon is about 30 feet (9.1 m.) above the Reagan sandstone), NE. J sec. 2, T. 2 S., R. 1 E., Ardmore 

 quadrangle (U. S. Geol. Sm'vey), Carter County; (12k) limestones of the Reagan sandstone (in the section 7 miles 

 (11.2 km.) north of Springer this horizon is about 225 feet (69 m.) above the porphyry contact and 55 feet (17 m.) 

 below the Arbuckle limestone), on the west side of Honey Creek, near the southeast corner of sec. 35, T. 1 S., 

 R. 1 E., Ardmore quadrangle (U. S. Geol. Sm'vey), Carter County; (12n) limestones of the Reagan sandstone (15 

 feet above 12k in the Springer section), NW. J sec. 1, T. 2 S., R. 1 E., Ardmore quadrangle (U. S. Geol. Survey), 

 Carter County; and (12p) about 225 feet (69 m.) above the igneous rocks in the limestones of the Reagan sandstone, 

 at the northwest extremity of the Arbuckle Mountains, about 4 miles (6.4 km.) east of Hojner, Carter County; all in 

 Oklahoma. 



(9q) About 10 feet (3 m.) above the porphyry contact and 90 feet (27.4 m.) below the Arbuckle limestone, in 

 limestones of the Reagan sandstone, in middle of W. J sec. 2, T. 4 N., R. 13 W.; (9p, 9r, and 9t)o, from 45 to 170 feet 

 (14 to 52 m.) above the porphyry contact, in the limestones of the Reagan sandstone, in SE. ^ NE. J sec. 2, T. 4 N., 

 R. 13 W.; (9s) about 85 feet (26 m.) below the Arbuckle limestone in the limestones of the Reagan sandstone, near 

 middle of W. ^sec. 13, T. 4 N., R. 13 W.; and (9u) about 195 feet (59.4 m.) above the porphyry contact in the lime- 

 stones of the Reagan sandstone in SE. \ NE. \ sec. 2, T. 4 N., R. 13 W.; all about 15 miles (24.2 km.) northwest of 

 Fort Sill, Comanche County, Oklahoma. 



(68) Interbedded sandstone and limestone, Packsaddle Mountain, Llano County, Texas. 



(54w) Limestone of the St. Charles formation [Walcott, 1908a, p. 6], about 250 feet (76 m.) above the Middle Cam- 

 brian on the north side of Twomile Canyon, near its mouth, 2 miles (3.2 km. ) southeast of Malade, Oneida; County, Idaho. 



Obolus ? torrentis Matthew. 



Obolus torrentis Matthew, 1902, Trans. Roy. Soc. Canada, 2d ser., vol. 8, sec. 4, No. 3, p. 94, PL I, fig. 1. (Mentioned 



as a new species.) 

 Obolus torrentis Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, p, 76, PI. VIII, fig. 1. 



(Described and discussed as a new species. Fig. 1 is copied from fig. 1 of the preceding reference.) 



The type material representing this form is too imperfect for specific determination. A 

 crushed and distorted dorsal valve, and the interior of a crushed ventral valve that suggests 

 Lingnlella triparilis (IMatthew) (PL XLV) are all Doctor Matthew sent me. Tlie difference in 

 stratigraphic horizon between the shales containing 0. ? torrentis and the shales bearing Lin- 

 gulella triparilis is not great, and but for the presence of an interbedded mass of "felsites" they 

 would probably have been considered as belonging to one formation. 



The specific name is derived from its occurrence near the great falls (torrent) in Dugald 

 Brook. 



Formation and locality. — Middle Cambrian: (13k) b Shales of Matthew's [1903, p. 15] Coldbrook, above the 

 great falls in Dugald Brook, Indian River, eastern Cape Breton, Nova Scotia. 



a 9r is the type locality. 



!> The specimens to which Locality 13k was assigned were collected one year later than those described by Doctor Matthew [1902, p. 94] 

 but from the same locality. 



