32 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



Surface apparently smooth with the exception of a few small, scat- 

 tered pustules on the glabella. 



At this same locality and horizon, and in limestone of the same 

 character but not in the same hand specimen, there is a number of 

 pygidia which appear to possess characteristics distinct from those of 

 any described species, and which have been referred to D. alastor. 

 They are of the same tj^pe as those that have been referred to D. tyj)l- 

 ealh. They are transversely semicircular in form, exclusive of the 

 spines on the border. Axis elongate conical, convex, divided by five 

 shallow furrows into five transverse, very slightly convex rings, and 

 a terminal section a little longer than the greatest width of any ring; 

 the terminal section ends someAvhat abruptly and slopes rapidly down- 

 ward to the margin; it is marked at the point where it slopes down- 

 ward by a small node each side of the center. Dorsal furrow very slight, 

 as the pleural lobes are nearly flat but slightly convex before reaching 

 the margin; the pleural lobes are divided by five shallow furrows into 

 a narrow frontal rim or segment and a posterior obscure segment; the 

 furrows and segments, with the exception of the anterior furrow and 

 segment, terminate at the inner margin of the border; the anterior 

 furrow crosses the border, and the anterior segment is continued out 

 across the border, merging into the anterior spine. Border flat, dis- 

 tinctly defined except opposite the anterior segment, and bordered 

 with a series of marginal spines; these include a long anterior spine, 

 which is a continuation of the anterior margin and a part of the first 

 segment; back of this there are four pairs of short spines which may 

 be considered in a general wa}^ as opposite the four anterior segments; 

 the sixth pair of spines project backward; they are long, broad, flat, 

 and opposite the obscure terminal segment of the pleural lobe; between 

 the two large spines, opposite the dorsal furrow at the side of the axis, 

 are two short spines; all of the spines are more or less flat and merge 

 directly into the flat border with the exception of the two anterior, 

 which are connected with the anterior segment and frontal rim. 



The surface of the rings and segments is marked b}^ minute granules; 

 otherwise it appears to be smooth under a strong lens. 



A specimen 7 mm. in length has a width of 12 mm., exclusive of the 

 spines; axis 3 mm. in width in front, 1.75 ram. at the posterior end; 

 pleural lobe back of the first segment 3 mm. in width. 



This species is characterized by the absence of a frontal limb on the 

 head, and the pygidium differs from that of DorypygeUa typicalis in 

 having a narrow axis, broad, flat margin, and in the arrangement of 

 the spines of the border. 



Forination and locality. — Middle Cambrian, central portion of 

 Chang Hsia formation, in hard, gray, fine-grained limestone; 3.25 

 miles southwest of Yen Chuang, Shangtung, China. 



Collected by Eliot Blackwelder, of the Carnegie Institution of 

 Washington Expedition to China. 



