776 CAMBRIAN BRACHIOPODA. 



interpolated beyond the umbo. Another transverse form has sunple strong ribs that increase 

 in number by the interpolation of a few new ribs. 



Brogger's illustrations of this species [1882, PL X, figs. 14a-c] suggest E. daunus more 

 than the typical form of E. christianise, as I understand and interpret it. "OrtJiis parva" 

 Dahnan (PI. XCVI, figs. 6, 6a-g) has sometimes been referred to E. christianise. 



Gagel [1890, p. 34] described the form usually found in the limestone, stating that the 

 surface is covered with strong, dichotomous ribs. He found it in drift blocks of the Ceratopyge 

 limestone near Belschwitz, East Prussia; and of glauconitic limestone near Prussian Holland, 

 and near Wehlau, East Prussia, Germany. 



Eoemer [1885, p. 36] calls attention in his description of the drift in the North German 

 plain to the fact that Remele [1885, pp. 695-698] was the first to identify with certainty blocks 

 of the Ceratoptjge limestone of Sweden in the drift of Germany, the presence of a form like E. 

 christianise being part of the evidence. This shell is probably E. daunus. Eoemer [1885, 

 p. 36] states in description of the Ceratopyge limestone that a small "Orthis if Orthis christianise 

 Kjeruh)" predominates. 



The specific name is derived from Christiania, Norway. 



Formation and locality. — Tipper Cambrian: (323x) Ceratopyge slate, at Russelohhen; and (323y) Ceratopyge 

 slate at Toien; both near Christiania, Norway. 



(310d.) Ceratopyge slate, at Borgholm, Oeland Island, Sweden. 



(309e) Shales of the Acerocare zone at Akarpsmolla, midway between K^gerod and Rost&nga, Province of Mal- 

 mohus, Sweden. 



y EOOBTHIS DAUNUS (Walcott). 

 Plate XCV, figures 2, 2a-c. 



Orthis sp. Remele, 1881, Zeitschr. Deutsch. geol. GeselL, Bd. 33, p. 696. (Characterized and compared in German.) 

 Orthis christianix Brogger (in part) [not Kjbrulf], 1882, Die silurischen Etagen 2 und 3, p. 48, PI. X, figs. 14a-c. 



(Mentions specimens from both the Ceratopyge slate and Ceratopyge limestone and thus probably includes the 



two species, Eoorthis christianix and E. daunus.) 

 Orthis christianix Roemek [not Kjerulf], 1885, Paleontologische Abhandlungen von Dames und Kayser, Bd. 2, Hft. 5, 



pp. 36, 37, and 38. (Mentioned in German, in review of literature.) 

 Orthis christianix Remele [not Kjerulf], 1885, Katalog der beim intern. Geologen-Congress zu Berlin ausgestellten 



Geschiebesaromlung, p. 6. (Locality mentioned.) 

 Orthis christianix Gagel [not Kjerulf], 1890, Beitr. zur Naturkunde Preuasens, von Physikal.-oekonom. Gesell. 



Konigsberg, No. 6, pp. 10 and 34, PI. II, figs. 22a-b. (Described and new localities mentioned in German.) 

 Orthis christianix Pompeckj [not Kjerulf], 1902, Neues Jahrb. fiir Mineralogie, Bd. 1, p. 7. (Occurrence mentioned, 



in German.) 

 Orthis (Plectorthis) daunus Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 261. (Characterized as a new species.) 

 Orthis {Plectorthis) daunus Walcott, Moberg and Segerberg, 1906, Medd. fran Lunds Geol. Faltklubb, Ser. B, No. 2 



(Aftryck ur K. Fysiografiska Sallskapets HandL, N. F., Bd. 17), p. 69, PI. II, figs. 2, 2a-c. (Characterized in 



Swedish. Figs. 2, 2a-c, in common with the remaining figures on PI. II of Moberg and Segerberg's paper, were 



copied from a preliminary photograph of PL XCV of this monograph.) 



The illustrations show the principal characters of this species. It differs from Eoorthis 

 christianise in having sunple ribs that increase in number toward the front and lateral margins 

 of the shell by interpolation of new ribs; no true bifurcation of the ribs was observed. A strong 

 median sinus occurs on specimens of the dorsal valve in both shale and limestone. The shell 

 is fibrous and impunctate. No traces have been seen of the fine, rounded, radiating stride that 

 occur on the broader ribs and interspaces of E. christianise. This species differs from E. wimani 

 in its more transverse form and less simple ribbing of the shell. 



Moberg and Segerberg [1906, pp. 69-70] regard this form as one of the variations of E. 

 christianix. This may be a correct view, but I am not prepared, after a careful study of the 

 material before me, to accept it. To support such an interpretation we should find, in a very 

 full series of E. christianise from the same bed or matrix, the gradations or varieties that I have 

 named tuUbergi and daunus. 



Formation and locality. — Passage beds between the Upper Cambrian and Ordovician: (386) Drift 

 blocks of Ceratopyge limestone near Belschwitz; (386a) drift blocks of "Glauconite limestone" near Prussian Holland, 



