4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



sense ; the umbilical slopes commonly set off from the lateral slopes 

 by angulations and the umbilical slope on the right side being very 

 slightly deeper than that on the left, but in some specimens, such as 

 the holotype, the sinistral twist is greater and the circumumbilical 

 angulation less pronounced; whorls three in number and the final ^ 

 whorl free; surface features including probable pseudo-selenizone 

 not well known but seemingly smooth except for lines of growth. 



Measurements 



Diameter Thickness 



The holotype (U.S.N.M. 114277) 24.3 mm. 12.8 mm. 



A figured paratype (U.S.N.M. 11427S) 13.7 mm. 6.4 mm. 



An unfigured paratype (U.S.N.M. 114281 a) . . 18.5 mm. 6.1 mm. 



Hypodigm. — Approximately 150 specimens. 



Remarks. — All specimens are in a light-brown calcareous sandstone 

 with rather coarse angular sand grains. The preservation is remark- 

 ably good for so coarse a matrix. Many specimens are broken free. 

 Great variation in relative thickness suggests that some specimens 

 may be compressed laterally; however the matrix seems to be one 

 that should resist compaction. The individual variation in other re- 

 spects such as skewness and the angularity of the circumumbilical 

 ridges suggests that individuals may vary in ratio of diameter to 

 thickness too. Individuals are very abundant, as many as 15 showing 

 on the surface of an oblong block approximately 6 cm. by 9 cm. Few 

 individuals (only 2 out of 150) reach the size of the holotype, most 

 of them being much smaller, narrower, and showing less skewness. 



Indeed, if the larger individuals did not show the skewness to so 

 much higher degree than the more abundant smaller ones, it might 

 have been missed. The specimens shown on plate i as figures le-g, 

 ih-j, ik-1, illustrate smaller specimens. 



Occurrence. — Sawatch formation, north side of Taylor Peak, 4 miles 

 south of Ashcraft, Colo. Collected about 100 feet above Archaean 

 rocks in 1891 by S. Ward Loper. Associated with the numerous 

 specimens of 5. major were specimens of Kingstonia loperi Resser, 

 Maryvillia loperi Resser (in both cases the types) and a specimen 

 identified by Dr. Christina Lochman Balk as "cf. Louchocephalus." 

 All of these indicate a Dresbachian fauna, early Upper Cambrian, 

 probably low in the Crepicephalus zone.^ 



1 Oral communication by Dr. C. L. Balk. 



