284 PROCEEDINGS OF THE NATIONAL MUSEVM. vol. xxviii. 



was punctate. The exterior form is like that of P. hUlingsi, but in 

 the surface ribs it differs from the latter and other described species 

 of the genus. 



A ventral valve has a length of 5 mm. ; width, 8 mm, A dorsal valve, 

 length, 7 mm.; width, 10 mm. There is considerable variation in the 

 relative proportions between length and width. 



Formation and locality. — Middle Cambrian. Dark argillaceous 

 shales, Wasatch Range, near Montpelier, Idaho. 



A similar shell occurs in the shaly limestone of the Middle Cambrian, 

 3 miles east of Antelope Springs, Utah. 



PROTORTHIS (?) NUNNEBERGENSIS, new species. 



Shell transversely semielliptical, plano-convex. Surface with very 

 line ribs tiiat increase by interpolation and bifurcation; on some shells 

 bands of slender ribs are delimited by stronger ribs, usually 2 to .5 

 between 2 more prominent ribs; tine concentric strire give a crenulated 

 aspect to the radiating ribs. Casts of the interior and exterior appear 

 to be minutely papillose, indicating puncttw in the shell. 



Ventral valve moderately convex, with the apex curved down to the 

 margin of the area; area and interior unknown. Dorsal valve flat or 

 very slightly concave between the umbo and margins; apex slightly 

 elevated above the plane of the surface and cardinal line; a median 

 sinus is present in some shells. 



Ohservations. — It is a little hazardous to refer this species to Protor- 

 this, as only the general form and surface are known. The nearly 

 plano-convex valves and surface relate it moi'e nearly to Protorthis 

 than Plectorthis^ and it does not appear to fall within Leptsena, 

 Rajinesquina,, or Strojyhomena. The specimens were collected by Mr. 

 Von Schmalensee in a dark, argillaceous shale above the Ceratopyge 

 limestone and below the lower graptalite shale. 



Format )on and locality. — Upper Cambrian. Mossebo, Nunneberg, 

 Vestergotland, Sweden. 



PROTORTHIS QUACOENSIS Matthew. 



Orlfm (juacoensis Matthew, Trana. Roy. Soc. Canada, III, 1886, p. 43, pi. v, 



figs. 20, 20a-c. 

 Orthis'! quacoemh Matthew, Trans. Roy. Soc. Canada, VIII, 1891, p. 131. 

 Protorthis quacoensk Hall and Clarke, Pal. N. Y., VIII, Pt. 1, p. 232, pi. vii 



A, fig. 21. 

 BillmgseUa (juacoensis ^cnvGHEKT, Bull. U. S. Geol. Sur., No. 87, 1897, p. 159. 

 Original description. — A small species. Subquadrate to semielliptical in outline, 

 broader than long, widest near or at the hinge line, which is not produced; moder- 

 ately convex, highest in the posterior third, flattened toward the front and sides. 

 Umbones not prominent. 



The dorsal valve rises rapidly from the hinge line, and has but a narrow, flattened 

 space at the angles. It is about one-third as high as it is long. The hipge plate has 

 a narrow area, which is striated lengthwise, and bears two tooth-like processes close 

 to the umbo, the point of which is bent down to the hinge line. 



