NO. 1395. CAMBRIAN BRACHIOPODA—WALCOTT. 273 



ial is too imperfect to base .specific determinations upon. Doctor 

 Pompcckj describes them as follows: 



(Plate XV, tig. «. ) 



Orlhh sp. — In the green Paradoxides slate of the Dlouha hora above the brook of 

 Zbirov near Skrej there were found some impressions oi dorsal valves, which dei)art 

 from Orth'i>i romingerl. The ribs are remarkably broad, Hat, and separated by 

 narrow intersjiaces; ribs may be observed to be split .several times. 



(Plate XV, fig. 7.) 



Orthissp. — The impression of a dorsal valve from green Paradox ides slate in the 

 gorge above Luh near Skrej also departs from Orthis romingeri by its greater breadth 

 and less distinct ribbing. 



ORTJSIA, new subgenus of OBTHIS. 



Ortliis lenticulark of authors is not an Orthis as restricted by Hall 

 and Clarke. ^ It appears to belong more nearly to the group of species 

 assembled under Plectorthis. It departs from Plectorthis in its very 

 thin shell, subequally convex valves, small umbonal cavity, and wide 

 variation in form and surface characters, and is here placed under a 

 new subgenus. 



The only species of the subgenus Orv-na is O. (O.) lenticidariH 

 which occurs in the Upper Cambrian. Another species that is doubt- 

 fully referred to the subgenus is O. ( (>. 'i) eurehensis a Middle Cambrian 

 form that appears to be nearer (). {().) Jentioularis than to other known 

 species of the genus Orthis. 



The species referred to Orusia are: 



ORTHIS (ORUSIA) LENTICULARIS Wahlenberg. 



Anomites lenticularis WAni,ENBER(i, Nova Acta Upsala, VIII, 1821, Petr. tell. 



Suec, p. 66. 

 Atrypaf lenticularis Dalman, Kongl. Utenskaps Acad. Hand., 1827, p. 1.32. 

 Spinfera lenticidaris Yoi^ Bucn, Abliandl d. Berl. Akad., 1834, p. 48, pi. i, figs. 



13, 14. 

 Atrypa? lenticularis Hisin(jer, Lethica Svecica, 1837, p. 7(5. 

 Atrypa lenticularis Kjerulf, Geol. d. siidl. Norw., 1857, p. 284; Veiviser ved. 



geol. exc. i. Christiania omegn., 1865, p. 3, fig. 7; Syd. Norges geol. atlas, 



1879, pi. XIII. 

 Orthis lenticularis Salter, Mem. (ileol. Sur. Great Britain, III, 1866, p. 339, pi. 



IV, figs. 8-10. 

 Orthis lenticularis Davidson, Geol. Mag., V, 1868, pi. xvi, figs. 20-22; British 



Foss. Brach., Ill, 1871, p. 230, pi. xxxiii, tigs. 22-28. 



«Pal. N. Y., VIII, Pt. 1, pp. 192-194. 



