506 CAMBRIAN BEACHIOPODA. 



growth, some of whicli are stronger than others. The shell is covered with small fine tubercles, in lines, like certain 

 species of Kingena from the Cretaceous, and produced by the fine, oblique, granular striae. (PI. XXXIX, fig. lie.)'' 



The internal molds (PI. XXXIX, fig. llb)o show clearly that the beaks were provided with a strong pedicle 

 furrow much like that of Lingulella davisi, to which these shells have considerable resemblance. The median septum 

 is well marked, likewise the depressions corresponding to the point of attachpient of the muscles of the pedicle (PI. 

 XXXIX, fig. lib)," and also the transmedian muscles. 



Observations: The Lingulella heberti is clearly related to lAngula attenuata Sowerby from the Llandeilo flags. 

 It is distinguished by the ornamentation of the shell, which recalls that of Lingulella granulata (Phillips). It should 

 also be compared with the form figured by Linnarsson [1876, PI. Ill, figs. 24^30] under the name of Lingulella ? 

 nathorsti, from the Paradoxides forchhammeri beds of Sweden. The latter is perhaps a little longer, but has a very 

 great resemblance to our shell. Mr. Davidson, who has kindly communicated to me the results of his examination of 

 this small shell, so abundant at the base of the Silurian sandstones of Cape Vidio, agrees with us in referring it to the 

 genus Lingulella; he believes that despite its resemblance to Lingulella davisi and L. granulata, it would probably 

 rank as a new species. It is dedicated to M. Hebert, to whom we owe so many discoveries in Pyrenean geology. 



Dimensions: Length, 8 to 10 mm.; breadth, 7 to 9 mm. 



Formation and locality. — Ordovician: (350a) Sandstones of the stage of Cabo Busto, in the cliffs of Cape Vidio, 

 Province of Oviedo; and (350b) sandstones of the stage of Cabo Busto, at Los Negros; both [Barrels, 1882, p. 186] in 

 northeastern Spain. 



Lingulella Helena (Walcott). 



Plate XXIV, figures 3, 3a-d. 



Obolus (Lingulella) helena Walcott, 1898, Proc. U. S. Nat. Mus., vol. 21, p. 406. (Described and discussed essen- 

 tially as below as a new species.) 



General form ovate, with the ventral valve obtusely acuminate, and the dorsal valve rounded 

 ovate. Valves moderately convex, as far as can be determined from their condition of preser- 

 vation in the shales. Surface of shell marked by rather strong lines of growth, and very fine 

 irregular, radiating, concentric strise that appear to inosculate, the surface having something 

 of the appearance of Obolus ■ (Westonia) ella (Hall and Whitfield). The character of the sur- 

 face marldngs of the inner layers and the interior of the shell is unknown. So far as can be 

 determined the shell is rather thin, and formed of a thin outer layer and one or more thin 

 inner layers or lamellae. A ventral valve 8 mm. in length has a width of 6 mm.; another 7.5 

 mm. in length has a width of 6 mmi. An associated dorsal valve 7 mm. in length has a width 

 of 5 mm. These variations in outline are to a considerable extent due to distortion. 



As shown in the cast of the interior of the shell, the area of the ventral valve is rather 

 long, and marked midway by a strongly defined cast of a pedicle groove, and midway between 

 that and the outer margin by a very distinct flexure line. The area of the dorsal valve is 

 rather long and quite distinctly marked on a cast of the interior. The cast of the interior of 

 the ventral valve shows a strong main vascular sinus (vs) on each side of the visceral area, 

 and in a cast of the dorsal valve a slight median septum is indicated, also traces of the main 

 vascular sinuses. The only traces of the muscle scars observed are the anterior laterals (j) 

 and a suggestion of the central scars in the dorsal valve. 



Observations. — Tliis species is associated with Obolus ( Westonia) ella (HaU and Whitfield) 

 in the siliceous shales near Helena, Montana, and what may be a similar form (PL XXIV, fig. 

 3d) occurs with the same species in Big Cottonwood Canyon, Utah, although the latter is quite 

 closely related to Obolus mcconnelli (Walcott). In form and surface characters it belongs to 

 the group of which Obolus {Westonia) ella may be taken as a type. It differs from 0. (W.) 

 ella in being narrower anteriorly and in its more acute beak. 



The specific name is derived from Helena, Montana, near which the type specimen was 

 collected. 



Formation and locality. ^Middle Cambrian: (30a) Shale on the north side of Big Cottonwood Canyon, 1 mile 

 (1.6 km.) below Argenta, Wasatch Range, southeast of Salt Lake City, Salt Lake County, Utah. 



(54s) Dark blue-gray Langston limestone [Walcott, 1908f, p. 198], just above the Cambrian quartzitic sandstones, 

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



(4n) Limestone about 325 feet (99.1 m.) above the unconformable base of the Cambrian in divide at the head 

 of Jackson Creek (locally known as Sheep Creek), a creek flowing into Jackson Lake about 0.5 mile (0.8 km.) south 

 of its northwestern corner, Teton Mountains, Grand Teton quadrangle (U. S. Geol. Survey), Uinta County, Wyoming. 



" Barrois's figures are copied in tUs monograph, and these references are to the figures which correspond with those mentioned by him. 



