OBOLID^. 469 



ObOLUS (WbSTONIA) ELLA ONAQUIENSIS Walcott. 

 Plate XLIX, figures 6, 6a. 



Obolus (Westonia) ella onaquiensis Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 67-68. (Discussed as 

 below as a new variety.) 



This variety is represented by a number of more or less imperfect specimens that at first 

 sight might be placed with Oiolus ( Westonia) ella (Hall and Whitfield), but the character of the 

 surface clearly distinguishes the two forms. In typical forms of 0. (W.) ella the transverse 

 striae are more regular, while in this variety they are in the form of sharp, finely zigzag, trans- 

 verse strise much like the shells of the species from the Bighorn Mountains. This surface is 

 formed by the interruption of very fine sharp ridges that curve from the umbo outward toward 

 the sides and front of the shell like engine-turned striae on a watch case. 



This form derives its varietal name from its occurrence in the Onaqui Range of Utah. 



Formation and locality. — Middle Cambrian : (33f) Shales about 400 feet (122 m.) above the Cambrian quartzitic 

 sandstones, on the western slope of the high peak southwest of Lookout Pass, Onaqui Range, west of Vernon, Tooele 

 County, Utah. 



Obolus (Westonia) elongatus Walcott. 



Plate LXIII, figures 8, 8a-d. ■ 



Obolus (Westonia) elongatus Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, p. 68, PI. VII, fig. 12. (Described 

 and discussed as below as a new species. Fig. 12 is copied in this monograph, PI. LXIII*fig. 8a.) 



General form elongate oval, with the ventral valve acuminate and the dorsal valve elongate 

 oval. Convexity unknown, as the shells are all flattened by compression. 



The outer surface is marked by fine concentric lines of growth crossed by a series of finely 

 denticulated, imbricating lines that start on each cardinal slope and extend obliquely forward 

 across the median line, and then curve out toward the sides of the shell; minute rhomboidal 

 spaces are formed over the posterior and central portions of the shell by the crossing of the 

 oblique lines; the denticulated margin faces forward and is seen only on the thin epidermal 

 layer, while the general system of oblique lines shows on both the outer layer and the next 

 iimer layer of the shell. 



The shell is built up of several thin layers or lamellae. The largest specimen of the ventral 

 valve has a length of 9 mm. ; width, 5 mm. ; a dorsal valve 6 mm. long has a width of 4 mm. 

 Nothing is known of the interior of these valves. 



Observations. — This is a more elongate species than Obolus (Westonia) bottnicus Walcott 

 and 0. (W.) fnlandensis Walcott. The oblique surface lines have the same general direction 

 as those of the latter species, but they are finely denticidated on their front margin, and cross 

 at the center at a greater angle. 



Formation and locality. — Middle Ordovician: (105x) Gray, siliceous shales, just below a band of quartzitic 

 •sandstones, probably corresponding in position to the upper part of the Simpson formation of the Oklahoma section, 

 Wasatch Canyon, east of Lakeview Ranch, about 5 miles (8 km.) north of Brigham, Boxelder County, Utah.' 



, Obolus (Westonia) escasoni (Matthew). 



Plate XLIX, figures 1, la-f. 



Lingulella (?) escasoni Matthew, 1901, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pt. 4, No. 19, pp. 270-273, PL V, 



figs. la-i. (Described and discussed as a new species. The specimens represented by figs. Id and Ig are redrawn 



in this monograph, PL XLIX, figs, lb and la, laa, respectively.) 

 Obolus (Westonia) escasoni (Matthew), Walcott, 1901, Proc. U. S. Nat. Mus., vol. 23, p. 691. (Merely changes generic 



reference.) 

 Westonia escasoni Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, pp. 206-209, PL XVI, 



figs. la-i. (Copied from Matthew, 1901a, pp. 270-273, PL V, figs, la-i.) 



General form ovate, with the ventral valve broadly subacuminate and the dorsal valve 

 rounded oval in outline. The valves are moderately convex, the ventral being most prominent 



