BILLINGSELLID^. 775 



EooETHis BAVARiCA (Barrandc). 



Plate XCVII, figure 4. 



Orthis bavarica Barrandb, 1868, Faune silurienne des environs de Hof , en Bavifere, p. 99, fig. 76. (Described in French 

 as a new species; see below for translation. Fig. 76 is reproduced in this monograph, PL XCVII, fig. 4.) 



Orthis bavarica Barrande, 1868, Neues Jahrb. fiir Mineralogie for 1868, p. 690, unnumbered plate, fig. 76. (Copy 

 of preceding reference.) 



Orthis sp., PoMPECKj, 1896, Tremadoc Fossilien bei Hof, p. 4. (Discussed in German; ^ee below for statement of 

 probable relationships.) 



The original description by Barrande follows : 



This very rare species is only represented by two specimens, reduced to a single valve, of which the less imperfect 

 of the two is figured. It has been deformed by compression, but we recognize that it represents the ventral valve, 

 the beak of which appears remarkably acute and projecting, doubtless by reason of compression. This valve shows 

 a barely indicated sinus, very shallow, but rather broad on the frontal contour. The surface is ornamented with 

 projecting longitudinal striae, close together, most of which end at the beak, but some are bifurcated in their exten- 

 sion. A trace of some concentric strise is seen. 



Length, 14 mm. ; breadth, somewhat reduced by compression, 9 mm. 



Pompeckj [1896a, p. 4] mentions the finding of two impressions of a species of Orthis 

 agreeing in form with E. iavarica (Barrande) at Neuhof, near Hof. The species differs in 

 having a sharper, higher rib intercalated between every three or four finer ribs, while the ribs 

 of E. havarica are all equally strong. The variation in the strength and number of the ribs 

 in species of Eoorihis is often so great that it may be that the form mentioned by Pompeckj 

 [1896a, p. 4] will prove to be only a variation of Eoorthis havarica. 



From the description and illustration, I think tliis species should be referred to Eoorthis. 



Formation and locality. — Passage beds between the Upper Cambrian and the Ordovician: (303c [Barrande, 

 1868a, p. 99]) suburbs of Hof; and (303f [Pompeckj, 1896a, pp. 7 and 8]) railway cut near Schellenberg, a little dis- 

 tance back of the railway station at Neuhof, near Hof; both in Bavaria, Germany. 



Eoorthis christiani^ (Kjerulf). 



Plate XCV,-figm-es 1, la-h. 



Orthis christianix Kjerulf, 1865, Veiviser ved Geologiske Excursioner i Christiania Omegn, p. 1 and figs. 8a-c, p. 3. 

 (Locality given in Norwegian.) 



Orthis christianix Kjerulf, Brogger (in part), 1882, Die silurischen Etagen 2 und 3, p. 48, PI. X, figs. 14a-c. (Men- 

 tions specimens from both the Ceratopyge slate and Ceratopyge limestone and thus probably includes the two 

 species, Eoorthis christianix and E. daunus. See below.) 



Orthis (Plectorthis) christianix (Kjerulf), Waloott, 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 260-261. (Discussed 

 somewhat as below.) 



Orthis (Plectorthis) christianix (Kjerulf), Mobbrg and Segerberg (in part), 1906, Medd. fran Lunds Geol. Faltklubb, 

 Ser. B, No. 2 (Aftryck ur K. Fysiografiska Sallskapets Handl., N. F., Bd. 17), p. 69, PL II, figs. 1, la-h; PL 

 III, figs. 12 and 13. (Described and discussed in Swedish. Includes Eoorthis daunus and E. tullbergi. Figs. 

 1, la-h, in common with the remaining figures on PL II of Moberg and Segerberg's paper, were copied from a 

 preliminary photograph of PL XCV of this monograph.) 



The general form and character of this shell as it occurs in the shales are shown by the 

 figures illustrating it. It appears to differ from any described species in the peculiarity of the 

 bifurcation of the radiating ribs. In all the species I have referred to Eoorthis the increase 

 in the number of ribs is by interpolation and not by true bifurcation. In E. christianise the 

 increase is by both methods, as shown by figures la, lb, and Ig. The reference to Eoorthis 

 is somewhat doubtful, as there are not sufRcient data to base a reference on the characters of 

 the interior, cardinal areas, or convexity of the valves. 



I have received a large number of specimens from Norway and Sweden labeled "Orthis 

 christianix." After a study of all the available material only the shells from the argillaceous 

 shale of Russelokken and Toien, Norway, and of Oeland Island, Sweden, appear to belong to 

 the species. The shells in the Ceratopyge limestone (Eoorthis daunus) have ribs that increase 

 in number by interpolation of ribs in the interspaces between the older ribs, and a second 

 species {E. wimani), that occurs in both the shale and the limestone, has simple ribs with few 



