68 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



Fragments of the pygidliim associated with the head show that it 

 had a slender, moderately convex axis, with more than 8 rings, and 

 that the pleural lobes were moderately convex, flattening out on a 

 broad, planulate margin, the furrows on the axis extending out across 

 the pleural lobes and nearly fading away on the broad margin; a faitit 

 trace of a very narrow, short pleural groove is shown on two of the 

 pleural segments. Surface of the pygidium slightly roughened l)y 

 w^hat appears to be, under a strong lens, a very tine granulation. 



Formation and locality. — Middle Cambrian. In gray crystalline 

 limestone, associated with Damesellablachwelderi; 3i miles southwest 

 of Yen Chuang, Hsin Tai, Shangtung, China. 



Collected by Eliot Blackwelder, of the Carnegie Institution of 

 Washington Expedition to China. 



PTEROCEPHALUS BUSIRIS, new species. 



This species is represented by two specimens of a pygidium that is 

 quite distinct from the pygidium associated with 1\ asiatlca. The 

 axis is elongate, slightl}^ convex, and converging uniformly to about 

 half its width at the posterior end; marked by eight or more narrow, 

 distinct, transverse furrows that divide it into eight or more trans- 

 verse rings and an elongate terminal portion. Pleural lobes slope 

 gently from the dorsal furrow down toward the margin; the}' are 

 marked b}^ the continuation of the distinct transverse furrows of the 

 axis, that extend oljliquel}' backward out to the margin, as far as can 

 be determined; there is a slight indication of a pleural groove on the 

 outer half of the pleural lobe. The pleural lobe is separated from 

 the broad border by a slight elevation of the point of union of the 

 border and pleural lobe, the slope of the two being approximatel}" the 

 same from the margin to the axis; a sharp ridge originates on the 

 front side of each pleural segment a little distance out from the axis, 

 and extends out across the border to the margin, leaving a concave 

 space between the sharp ridges over the entire extent of the liorder; 

 from the elongate terminal segment of the axis a narrow, double ridge 

 continues backward to the border, which is here slightly incurved. 



Surface flnely granular under a sti'ong lens. 



This species difl'ers from P. asiatlca in the form of the segments of 

 the pleural lobes and margin. 



Formation and lorality. — Upper Can\])rian, lower portion of Chao 

 Mi Tien formation, in dark, compact limestone; 3 miles southwest of 

 Yen Chuang. Hsin Tai, Shangtung, China. 



A specimen referred to this species also occurs in the lower portion 

 of the ('hao Mi Tien formation, two-thirds of a mile west of Tai An 

 Fu, in Shangtung, China. 



Collected by Eliot Blackwelder, of the Carnegie Institution of 

 Washington Expedition to China. 



