788 CAMBRIAN BRACHIOPODA. 



(73 m.) above the porphyry contact and 40 feet (12 m.) below the Arbuckle limestone), NW. J sec. 1, T. 2 S., R. 1 E.; 

 both in the Ardmore quadrangle (U. S. Geol. Survey), Carter County, Oklahoma. 



(153a) Limestone in ravine on west side of Dry Creek, near the mouth of Pass Creek, about 5 miles (8.1 km.) north 

 of Hillsdale, Threeforks quadrangle (U. S. Geol. Sm-vey), Gallatin County, Montana. 



(14b) Limestone on Cold Creek at north end of gorge opposite the north end of Sponge Mountain, 2 miles (3.2km.) 

 south of the San Saba County line, in Llano County; (68) interbedded sandstone and limestone, Packsaddle Mountain, 

 Llano County; and (71) limestone in Cold Creeh Canyon, Burnet County; all in Texas. 



Specimens that are somewhat doubtfully referred to this variety occur at the following 

 locahties : 



Upper Cambrian : (lid) Arenaceous limestone about 2 miles (3.2 km.) north of Montana, in sec. 22, T. 35 N., R. IE., 

 Iron County; and (11 1) arenaceous limestone of the Elvins formation, 50 feet (15.2 m.) above the "Edgewise beds," St. 

 Francois County; both in Missoiui. 



EOOETHIS REMNICHA WINFIELDENSIS (WalcottJ. 



Plate XCI, figures 2, 2a-e. 



Orthis (Plectorthis) remnicha vAnfieldensis Walcott, 1905, Pror. U. S. Nat. Mus., vol. 28, p. 270. (Characterized as 

 below as a new variety.) 



This variety is characterized by having finer and more uniform costse than any of the shells 

 referred to Eoorihis remnicha (N. H.WincheU). The costse increase by interpolation rather than 

 bifurcation in the true sense of the word. The shorter costse begin as very narrow, sharp 

 ridges, merging into the sides of the larger costsB below the summit of the latter, or they may 

 arise entirely on the interspaces between the costse. The pseudospondylium is less strongly 

 developed than in E. remnicha. The young shells are usually narrower at the hinge line than 

 the adult; but this feature is sometimes present in large shells (PL XCI, fig. 2c). 



The varietal name is derived from Winfield, Wisconsin. 

 Formation and locality. — Tipper Cambrian: (97a) "St. Croix sandstone" near Winfield, Jefferson County; and 

 (99a) "St. Croix sandstone" near Pilot Knob, Adams County; both in Wisconsin. 



A specimen which is somewhat doubtfully referred to this variety occurs in the following 

 locality : 



Upper Cambrian: (83) "St. Croix sandstone" at Trempealeau, Trempealeau County, Wisconsin. 



/ EooRTHis SALTENSis (Kaj^scr). 

 Plate XCVII, figure 11. 



Orthis saltensis Kaysbe, 1876, Beitrage zur Geologie und Paleontologie der argentinischen Republik, vol. 2, Pale- 

 ontologischen Theil; Abth. 1, p. 8, PI. I, figs. 15, 16. (Described and discussed in German as a new species; see 

 below for translation. Figs. 15 and 16 are reproduced in this monogi-aph, PI. XCVII, figs. 11' and 11, respec- 

 tively.) 



Orthis saltensis? Kayser, 1897, Zeitschr. Deutsch. geol. Gesell. for 1897, Bd. 49, Heft 2, No. 2, p. 280. (Mentioned in 

 German from new localities.) 



Orthis (Plectorthis) saltensis (Kayser), Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 271. (Characterized.) 



The original description by Kayser follows : 



Shell nearly circular in outline, with straight hinge edge, which is about equal to three-fourtlis of the greatest 

 breadth of the shell, measured approximately across the middle. Ventral valve moderately and uniformly arched, 

 with a faint keel rising in the middle. Beak short, slightly curved. Dorsal valve slightly arched, with a median 

 depression which is flat but becomes rather broad, starting at the umbo. The surface of both valves is covered with 

 fine but plainly marked ribs, united into bundles, the lateral ones bending somewhat outward. 



In the sandstones in the province of Salta this species fills whole beds. At the town of Salta it occurs alone. At 

 the Nevado de Castillo it is accompanied by Lingula. At both localities it occurs as impressions and casts, and as 

 white, well-preserved shell, peeling off in flakes. Finally it also occurs, associated with trilobites, Eyoliihes, and 

 other Orthis species, at Tilcuya in the province of Jujuy, but there it is without calcareous shell. I know only one 

 primordial Orthis with which this fine species might be compared, namely Orthis inenapix Hicks [of. Davidson, 1869, 

 PI. XXXIII, figs. 8-12], from the English Arenig group. In this, however, the ribs show less tendency to arrange 

 themselves in bundles, the sinus is narrower, and the ventral valve is much more strongly keeled. 



Kayser's description and figures [1876, p. 8, PI. I, figs. 15-16] lead me to refer this species 

 to the genus Eoorthis. The general form of the valves, the casts of the interior of the ventral 



