82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 55 



Genus ACROTHELE Linnarsson [1876, p. 20] 

 ACROTHELE ARTEMIS, new species 



Plate 8, Figure; 10 



General form of ventral valve moderately convex ; subcircular 

 and somewhat obtusely acuminate in outline ; apex near the pos- 

 terior margin; pedicle opening unknown, but from the occurrence 

 of a small boss on the inside of the shell beneath the apex, it was 

 probably of the same character as in closely related species. 



Surface marked by concentric lines and small ridges of growth 

 and an irregular system of fine granules on the concentric ridges ; 

 in the lower interspaces there is an irregular distribution of very 

 minute inosculating ridges that, with the tubercles, forms a surface 

 independent of the concentric growth lines. The shell is built up of 

 numerous lamellse beneath the outer surface layer and appears to- 

 have been corneous or composed of phosphate of lime and chitin. 

 The largest shell has a length and wadth of 10 mm. ; the apex is 

 about 2 mm. from the posterior margin ; dorsal valve unknown. 



Observations. — This species resembles in form Acrothele prima 

 costata (Alatthew) [1895, p. 128], and both species have a granular 

 surface. The latter species, however, has a thinner shell and its 

 surface is marked by much larger granules. I do not know of anr 

 other closely related species. 



Formation and Locality. — Middle Cambrian : Dark-blue lime- 

 stones of the Langston formation just above the Cambrian quartzitic 

 sandstone beds on the north side of Two Mile Canyon near its 

 mouth, 2 miles (3.22 km.) southeast of Malad, Oneida County,. 

 Idaho. 



ACROTHELE BELLAPUNCTATA, new species 



Plate 8, Figures 9 and 9' 



General form a broad transverse oval, with the posterior side 

 slightly flattened and arched upward for a short distance below the 

 apex. Ventral valve convex near the umbo and nearly flat over the 

 anterior portion of the valve ; apex near the posterior margin. 

 Foraminal aperture apparently at the apex above a short, not dis- 

 tinctly marked false area. Ventral valve nearly flat and with the 

 posterior margin curved downward so as to fill the space caused by 

 the upward arching of the margin of the ventral valve. Surface of 

 shell beautifully ornamented by elevated sharp oblique lines with 

 deep interspaces that give a strongly punctate appearance to the 



