454 CAMBEIAN BRACHIOPODA. 



Obolus (Westonia) bottnicus (Wiman). 

 Plate XLVIII, figures 4, 4a-c. 



Lingula bottnica Wiman, 1902, Bull. Geol. Inst. Univ. Upsala, vol. 6, pt. 1, No. 11, p. 51, PL II, figs. 4CM4. (Charac- 

 terized and discussed in German as a new species. The specimens represented by figs. 41, 42, 43, and 44 are 

 redrawn in this monograph, PI. XLVIII, figs. 4, 4a, 4b, and 4c, respectively.) 



Obolus (Westonia) bottnica (Wiman), Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 335-336. (Characterized and 

 discussed as below.) 



The description of Oholus (Westonia) finlandensis Walcott so closely applies to this species 

 that it is only necessary to point out the difference between the two and to compare the figures 

 illustrating them. 



The surface of Oholus (Westonia) hottnicus has the same concentric and radiating lines with 

 the irregular, transverse lines terminating at right angles to the margins, curving inward and 

 backward in such a manner as obliquely to cross the radiating lines that extend frona the umbo 

 forward to the anterior and anterolateral margins. The central scars of the dorsal valve are 

 much farther forward in 0. ( W.) hottnicus. 



Wiman [1902, p. 51] refers this species to the Olenellus sandstone series. The bowlder 

 containing it also carried Aparchitesf anderssoni, Hipponicliarion matthewi, Acrqtreta egge- 

 grunSsnsis, Kutorginaf, Torellella Isevigata, and fragments referred to Olenellus. This fauna 

 is essentially Middle Cambrian in its facies and unless the fragments referred to Olenellus are 

 indisputably of that genus, I am inclined to refer the bowlder and its contained fossils to the 

 Middle Cambrian. The fact that Oholus (Westonia) hottnicus is nearly identical with 0. (W.) 

 finlandensis of the Middle Cambrian of Finland also points to the Middle Cambrian age of the 

 fauna. 



The specific name is derived from the Swedish form of the word Bothnia. 



Formation and locality. — Middle? Cambrian:' (311) Drift bowlder of coarse-grained, somewhat friable, glauconitic 

 sandstone, No. 3 [Wiman, 1902, p. 57], on Eggegrund Island, about 25 miles (40 hm.) east-northeast ofGefle, Province of 

 Oefleborg, Siveden. 



Specimens which were doubtfully referred to this species by Wiman occur at the following 

 locality : 



Middle? Cambrian: (3He) Drift bowlder of rusty sandstone [Wiman, 1902, p. 57], south of Lumparn, parish 

 of Jomala, Aland Island, Finland, Russia. 



Obolus (Westonia) chuaeensis (Walcott). 



Plate XXV, figures 2, 2a-e. 



Obolus (Lingulella) chuarensis Walcott, 1898, Proc. U. S. Nat. Mus., vol. 21, p. 399. (Described and discussed 



essentially as below as a new species.) 

 Oholus ( Westonia) chuarensis Walcott, 1901, Proc. U. S. Nat. Mus., vol. 23, p. 691. (Merely changes generic reference.) 



General form broadly ovate, almost subquadrate, with the ventral valve obtusely acunainate, 

 and the dorsal valve rounded subquadrate, the posterior margin being broadly obtuse ; convexity 

 m.oderate, increasing somewhat in the older shells. Surface of shell marked by rather strong, 

 concentric lines and strife of growth and very fine, more or less transverse and irregular, appar- 

 ently imbricating strife such as ornament the surface of Oholus (Westonia) ella (Hall and Whit- 

 field) and 0. (W.) euglyplius (Walcott). Fine radiating striae also appear under a strong 

 magnifying glass. Wlien the outer surface is exfoliated the inner layers of the shell show 

 traces of radiating strife. The inner surface is marked by pits or punctse, arranged in more or 

 less irregular concentric lines; also fine radiating strife. The shell is strong and formed of a 

 thin outer layer and several inner layers or lamellae, those near the outer margin being arranged 

 obliquely to the outer surface. 



The only traces of the interior markings are those on the casts of the dorsal valve. These 

 show a short and rather broad area, strong vascular sinuses, and traces of the anterior lateral 

 muscle scars. 



