NO. 1395. CAMBRIAN BRACHIOPODA—WALCOTT. 335 



OBOLUS (WESTONIA) BLACKWELDERI, new species. 



General form elongate, with the width about one-half the length; 

 front margin broadly rounded; sides slightly arched up to the lateral 

 slopes which are quite straight in the ventral valve and curved toward 

 the rounded posterior end of the dorsal valve; the beak of the ventral 

 valve is pointed and marginal. The convexity of the valves i*.s mod- 

 erate, that of the dorsal apparently being the greater. Surface 

 marked by concentric strife and lines of growth which are crossed by 

 irregular, fine, imbricating, more or less transverse lines; the trans- 

 verse lines trend slightl}' backward toward the sides of the valves. 

 A dorsal valve 8 mm. in length has a width of 5 mm. 



Ohsei'i^ations. — Nothing is known of the interior of the valves. 

 When the shell is broken from the limestone, the outer surface usu- 

 ally adheres to the matrix. The best exteriors are those of shells on 

 the surface of the layers. Of the known species of Westonla^ 0.{W.) 

 wimani and 0. ( ^Y.) haltica are most nearlj' related to O. ( W.) hlacJi- 

 welderi. The latter is a larger shell and also less narrow proportion- 

 ally where the gently arching sides pass into the postero-Iateral slopes. 



Formation and locality. — Middle Cambrian. Chang Hsia limestone. 

 Two, and two and one-half miles south of Yen Chuang, Shantung, 

 China. 



Collected by Mr. Eliot Blackwelder of the Carnegie Institution 

 expedition to China. 



OBOLUS (WESTONIA) BOTTNICA Wiman. 



Lingula hottnica Wiman, Bull. Geol. Institute, Upsala, Xo. 2, VI, 1903, Pt. 1. 

 Studien Nordbaltisehe Silurgebiet, p. 51, pi. ii, figs. 40-4-1. 



The description of O. {We-stonia) finlaiidends so closelv applies to 

 the description of this species that it is only necessary to point out the 

 difference between the two. 



The surface of 0. (Weston la) hottnica 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 to obliquely cross the radiating lines that extend from the umbo 

 forward to the anterior and antero-lateral margins. The central scars 

 of the dorsal valve are much further forward in 0. ( Westonla) hottnica. 



Formation and loccdlty. — Middle? Cambrian. Coarse grained, 

 somewhat friable, glauconitic sandstone, drift bowlder No. 3 on 

 Eggegrund Island, North Baltic. 



Dr. Carl Wiman refers this species to the Olenellus sandstone series. 

 The bowlder containing it also carried Aparchltesf andet^smni.^ Hip- 

 jyonicTiarlor niattheivl, Acretreta eggegrundensls., Kvtorginaff U^relleUa 

 Isevlgata, and fragments referred to Olenellxis. This fauna is essen- 

 tially Middle Cambrian in its facies, and unless the fragments referred 



