730 CAMBRIAN BRACHIOPODA. 



is more transverse; the delthyrium is also larger. Nisusia rara occurs at the same stratigraphic 

 horizon as Nisusia alberta (Walcott), but it differs from the latter in having a larger delthyrium 

 and a strong and deep median sinus. 



The surface of N. rara is marked by rounded radiating ribs that increase by interpolation 

 and bifurcation; small nodes on some of the ribs indicate the presence of spines on the outer 

 surface. A portion of a convex deltidium is shown that has the outer portion broken away. 

 The type specimen has a length of 8 mm.; width, 16 mm. 



Formation and locality. — Middle Cambrian : (55o) Spence shale member of the Ute limestone [Walcott, 1908a, 



p. 8], about 50 feet (15.2 m.) above the Brigham quartzite and 2,755 feet (839.7 m.) below the Upper Cambrian, in 



a ravine running up into Danish Flat from Mill Canyon, about 6 miles (9.6 km.) west- 



^^_^^^ ^j^MR^ southwest of Liberty and 15 miles (24.2 km.) west of Montpelier, Bear Lake County, 



■H^^^^^^Hh Nisusia? vaticina (de Verneuil and Barrande). 



^B^^K^^^F ^^^^<^ XCYII, figures 3, 3a-b. 



■^^^^ OrtMsina vaticina de Verneuil and Barrande [not Salter MS.], 1860, Bull. Soc. 



FIGURE 60 -ifi^smmra Walcott .^j_ ^^ 2d ser., vol. 17, pp. 533-535, PI. VIII, figs. 8, 8a-d. (Described 



Cast of the interior of a dorsal , ,• j ■ t^ ,. • t, i ? .^ , ^- t^- „ 



valTe(U. S.Nat. Mus. Cat. No. 8,nd discussed in Irench as a new species; see below lor translation, ligs. 8, 



52295a, labeled 52295b [Walcott, 8b-c are copied in this monograph, PI. XCVII, figs. 3, 3a-b, respectively.) 



I908d, p. 123] by error).a OrtMsina vaticina de Verneuil and Barrande, Mallada, 1875, Bol. Com. Mapa Geol6gico 

 The specimen represented is Espafia, tome 2, p. 32. (Mentioned.) 



from Locality 55c, Middle Cambrian 



Spence shale, near Liberty, Idaho. The Original description by de Vcmeuil and Barrande follows: 



The figure is copied from Walcott 



[l908d, PI. IX, fig. 13a]. Shell subquadrangular, slightly emarginate below the lateral extremities. Length 



equal to three-fourths of the breadth. Hinge ridge somewhat shorter than the greatest 

 width of the shell. Ventral valve twice as thick as the dorsal, area double in height. Triangular opening on each 

 of the valves, covered in part by a deltidium. At the point of the beak there is a very fine opening, hardly visible, 

 which is obliterated in certain specimens. The valves are regularly bulged and have no marked sinus, so that 

 their edge is straight. The surface is ornamented with fine, dichotomous, spiny striae; these spines, or tubes, which 

 are 1 or 2 mm. long on the ventral valve, are hardly seen on the other valve. At 10 mm. from the beak, where 

 the striae subdivide by dichotomy, six of them are counted in a space of 5 mm. 



Dimensions: Length, 18 mm.; breadth, 24 mm.; thickness, 8 mm. 



Relations and differences: This species belongs to the Orthis group, united by one of us under the name of Redo 

 striatx b and which Davidson includes in the genus Orthisina of d'Orbigny.c The two characteristics of this group 

 consist in the direction of the striae, which, starting from the beak, never curve backward to reach the hinge crest, 

 and in the presence of a deltidium which covers the triangular cleft of the area. The hole with which this deltidium 

 is sometimes pierced, a characteristic on which d'Orbigny established the genus Orthisina, is of altogether secondary 

 importance, for it appears to be only temporary. We have demonstrated that in certain Leptsenae, which have an 

 opening analogous to that of the species under discussion, that characteristic produces no significant change in the 

 internal apparatus."^ 



In having its striae provided with tubes or spines this species is distinguished from all others, except 0. striatula, 

 with which it is impossible, on other accounts, to confound it. It may be compared either to 0. romingeri Barrande, 

 from the primordial zone of Bohemia, which is distinguished by a rather pronounced sinus on the small valve, a more 

 prominent beak and smooth striae; or with 0. inflexa Pander, from the lower Silurian strata of St. Petersburg, which 

 is thicker, as observed especially in the dorsal valve, which in this respect is almost equal to the opposite valve. 

 Moreover the striae of the Russian species are never spinous. 



Mr. Salter, whose kindness is never appealed to in vain, thought he recognized in our specimens a species found 

 recently in the Lingula beds, to which, in the collection of the museum of practical geology at London, he gave the 

 name 0. vaticina, under which we publish it. 



Observations. — In appearance this shell is closely related to Lower Ordovician species of 

 Clitamhonites that have a fimbriated surface. If, as the authors state, many of the shells are 

 imperforate, then it is probable that the species is closely related to and belongs with Nisusia, 

 although the illustration of the spines indicates that they were of a different character from 

 those of Nisusia festinata (Billings). In the presence of the statement that the shells are 

 associated -with, the Primordial fossils {Paradoxides, etc.) and the absence of an opportunity to 



a See the note accompanying the first reference in the synonymy of EooTthis thyonp, p. 789, and the note following text figm-es 70A-C, p. 789. 

 6 Murchison, de Verneuil, et de Keyserling, G^ologie de la Eussie d'Europe et de I'Oural, vol, 2, 1845, p. 179. Bull. Soc. geol. France, 2d ser., 

 vol. 2, 1845, p. 481. 



c Davidson, Introduction h I'histoire naturelle des brachiopodes, French translation by Deslongchamps, p. 130. 

 i De Verneuil, Bull. Soc. g§ol. France, 2d ser., vol. 5, 1848, p. 348. 



