OBOLIDiE. 451 



(Wliitfield), 0. (IF.) rogersi (Walcott), 0. (TF.?) lamellosus (Barrande), and 0. (TF.) escasoni 

 (Matthew) all have transverse, irregular, elevated lines. In 0. (W.) stoneanus and 0. (W.) 

 rogersi these lines have two or three sharp undulations near the median line, and in 0. (W.) 

 aurora many short and more or less irregular undulations occur on the entire central portion of 

 the shell. Beyond the short, central undulations, more or less wave-like, long undulations extend 

 to the sides of the valve, usually with a slight backward curvature toward the margin. 



Oholus (Westonia) Jinlandensis Walcott, 0. (W.) lottnicus (Wiman), and 0. (W.) wimani 

 Walcott, of the Middle (possibly Lower) Cambrian sandstones of Sweden, differ in surface 

 characters from the typical species of the genus. In these species the concentric lines and strise 

 of growtli are weU marked, also radiating hnes that extend from the umbo irregularly toward 

 the front and side margins of the shell. In addition there is a series of somewhat irregular 

 striae or lines that terminate at right angles to the lateral margin, start in toward the center of 

 the sheU, and then curve backward so as to meet at the center, or merge apparently into the 

 radiating striae (PI. XL VIII, figs. 3 and 3a). These lines were apparently formed by the same 

 agency (the front margin of the mantle) that formed the various irregular, more or less trans- 

 verse lines on the other species of the genus. The two other species from the sandstones of 

 Sweden, 0. ( W.) dlandensis Walcott and 0. ( W.) halticus Walcott, appear to have the typical 

 Westonia surface represented on 0. ( W.) ella, although it is exceedingly fine. 



The generic name was given in honor of Mr. T. C. Weston. 



Obolus (Westonia) alandensis Walcott. 

 ^ Plate XL VIII, figures 6, 6a. 



Lingular sp. No. 2, Wiman, 1902, Bull. Geol. Inst. Univ. Upsala, vol. 6, pt. 1, No. 11, p. 52, PI. II, fig. 39. (Locality 



given.) 

 Lingulella ? sp. No. 3, Wiman, 1902, idem, p. 52, PI. II, fig. 33. (Locality given. The specimen represented by iig. 33 



is redrawn in this monograph, PL XL VIII, fig. 6.) 

 Lingulella '? sp. No. 5, Wiman, 1902, idem, p. 52, PI. II, fig. 35. (Locality given. The specimen represented by fig. 35 



is redrawn in this monograph, PL XLVIII, fig. 6a.) 

 Obolus {Westonia) alandensis Walcott, 1905, Proc. IT. S. Nat. Mus., vol. 28, p. 334. (Discussed essentially as below 



as a new species.) 



This species is characterized by its broad form when compared with Oholus ( Westonia) 

 hottnicus (Wiman), 0. ( W.) wimani Walcott, and 0. ( W.) halticusWalcott. Its surface is marked 

 by fine concentric lines of growth, with very fine, threadlike, concentric striae between them. 

 In strong, reflected light, almost microscopic, transverse, very irregular lines can be seen that 

 give the surface somewhat the appearance of that of 0. (W.) ella (Hall and Whitfield). 



For reference to the geological horizon of bowlders on Eggegrund Island, similar to the 

 ones containing this species, see description of 0. ( W.) hottnicus Walcott, p. 454. 



The species derives its specific name from its occurrence on Aland Island. 



Formation and locality. — Middle? Cambrian: (SXlj and 311k) Drift bowlders of bituminous sandstone, Nos. 

 28 and 29 [Wiman, 1902, p. 57], on Biludden, about 20 miles (32.2 km.) east of Gefle, Province of Gefleborg; 

 and (311m) drift bowlder of bituminous sandstone, No. 1 [Wiman, 1902, p. 57], on Limon Island, about 12 miles (19.3 

 km.) northeast of Gefle, Province of Gefleborg; all in Sweden. 



(311y) Drift bowlder of rusty sandstone [Wiman, 1902, p. 57], at Ytternds, Slevnnern, Aland Island, Finland, Russia. 



Obolus (Westonia) axiroea (Hall). 

 Plate XLVI, figures 1, la-h. 



Lingula aurora Hall, 1861, Rept. Supt. Geol. Survey Wisconsin, p. 24. 



Lingula aurora Hall, 1862, Rept. Geol. Survey Wisconsin, vol. 1, p. 21, fig. 4. (No text reference.) 



Lingula aurora Hall, 1863, Sixteenth Ann. Rept. New York State Cab. Nat. Hist., pp. 126-127, PL VI, figs. 4 and 5. 



(Described and discussed.) 

 Lingula aurora Hall, 1867, Trans. Albany Inst., vol. 5, pp. 103-104, PL I, figs. 4 and 5. (Copy of preceding reference.) 

 Lingulella aurora Hall, 1873, Twenty-third Ann. Rept. New York State Cab. Nat. Hist., pp. 244-245. (Merely 



changes generic reference . ) 



