456 CAMBRIAN BRACHIOPODA. 



Lingulella ella (Hall and Whitfield), Hall and Clarke (in part), 1892, Nat. Hist. New York, Paleontology, vol. 8, 



pt. 1, p. 58, figs. 19 and 21 (not fig. 20, now referred to Lingulella dubia). (Species discussed in the text. Figs. 



19 arid 21 are copied from Walcott, 1886b, PL VII, fig. 2, and PL VIII, fig. 4a.) 

 Lingulepis ella Hall and ^Vhitfield, Walcott, 1897, Am. Jour. Sci., 4th ser., vol. 3, p. 404. (Merely changes generic 



reference.) 

 Obolus {Lingulella) ella (Hall and Whitfield), Walcott, 1898, Proc. U. S. Nat. Mus., vol. 21, PL XXVIII, figs. 5-8. 



(No text reference. The specimens represented by figs. 5-8 are redrawn in this monograph, PL XLVII, 



figs. Ig, Ik, Id, and li, respectively.) 

 Obolus (Westonia) ella (Hall and "Whitfield), Walcott, 1901, Proc. U. S. Nat. Mus., vol. 23, p. 691. (Merely changes 



generic reference.) 

 Obolus ella (Hall and ^^Tiitfield), Matthew, 1902, Trans. Roy. Soc. Canada for 1902, 2d ser., vol. 8, sec. 4, No. 3, pp. 96 



and 110, PL I, figs. 9a-b. (Discussed on both pages.) 

 Lingulella ella (Hall and AVhitfield), Pack, 1906, Jour. GeoL, vol. 14, No. 4, p. 295, PL I, figs. 2 and 2a. (Mentioned, 



and new localities given.) 

 Lingulella {Westonia) ella (Hall and Whitfield), Grabau and Shimer, 1907, North American Index Fossils, vol. 1, 



p. 193, figs. 229a-b. (Described. Figs. 229a-b are copied from Walcott [1886b, PL VIII, figs. 4 and 4a, 



respectively].) 



General form broad ovate, with the dorsal valve subquadrate or rounded quadrate and 

 the ventral valve obtusely acuminate; valves moderately convex, so far as can be determined 

 from the crushed and flattened specimens from the shales of Utah and Nevada. Surface of 

 the shell marked by concentric striae and lines of growth and, oh the type specimen, by very 

 fine, irregular, lamellose, more or less transverse strise and fine radiating lines; the siirface is 

 much like that of 0. ( W.) euglyphus (Walcott) (PI. XL VIII) ; fine, clearly defined radiating 

 lines occur on the inner layer of the shell of partly exfoliated specimens. The cast of the inner 

 surface of the shell shows papilla that filled punctse in the shell; they are rather large and are 

 arranged in the central portion of the shell in concentric lines, much as in Lingulella davisi. 

 The shell is strong and rather thick in old shells. It is made up of a thin outer layer and several 

 inner layers or lamellae that are well shown in the figure of the type specimen (PI. XLVII, 

 fig. lb). 



The largest ventral valve thus far examined has a length of 16 mm. and a width of 13 mm. 

 A dorsal valve is 13 mm. long by 12.5 mm. in width. 



The area of the ventral valve is of the same type as that of 0. ( IF.) aurora (Hall) (PI. 

 XL VI) and Lingulella ampla (Owen) (PL XXVIII). The flexure line is nearer the pedicle fur- 

 row than in Lingulella perattenuata (Wliitfield) (PI. XXI), L. acutangula (Roemer) (PL XVII), 

 Lingulella ampla, and Obolus ( Westonia) aurora, which resvilts in a wider outer lateral space on 

 the area (PL XLVII, fig. Ic (a')). The pedicle furrow is strong and deeply rounded, and in 

 one specimen referred to this species (PL XLVII, figs. Id and Ig) the cast of the base of the 

 undercut between the area and the outer shell is clearly shown on each side of the pedicle groove. 

 The area of the dorsal valve is low and broad; the flexure lines cross it so as to form a broad, 

 shghtly elevated space in the cast corresponding to a broad, shallow furrow in, the shell (PL 

 XLVII, fig. li). The strife of growth cross the area parallel with its base, both in the ventral 

 and dorsal valves. 



The cast of the interior of the ventral valve shows the visceral cavity (PL XLVII, figs. Ic, 

 Id, and Ig) and the median septum of the dorsal valve is seen in figures li and Ik. 



The muscle scars are not distinctly shown on the ventral valve. In the dorsal valve the 

 central scars (h) are preserved in specimens from Nevada (fig. li) and Montana (figs. 1 and Ik), 

 and the anterior laterals in Plate XLVII, figures Ik and 1 1. 



The remains of markings made by the vascular system are limited to the main or trunk 

 sinuses of the two valves, and a portion of the parietal scar (ps) is seen on one specimen of the 

 ventral valve (PL XLVII, fig. Ig). 



Observations. — The type specimen of this species is a somewhat crushed dorsal valve that 

 fortunately preserves the outer surface and much of the shell. Near the type locality, and 

 in the same band of slaty shales, were found a number of specimens, including a series of young 

 shells. Two of the larger shells are shown by Plate XLVII, figures 1 and la, and two of the 



