Vol I. Sun — Cambrian Fnunan of North China (iv) 3S 



tion, frontal rim flat ard marked by short spines. The posterior third seems to be 

 defined by broad shallow slightly arched backward converging transverse depressions. 



Associated pygidium transversely semicircular, with a spinose margin and 

 strongly convex axis narrowing backwards at a moderate rate, and devided by shallow 

 but sharp transverse furrow into four rings and a broader terminal lobe. Only part of 

 the first anterior ring is shown, and the other rings are not well defined. 



Limb almost flat except for abruptly decending marginal portion, the furrows 

 crossing the axis prolonged on the limb deviding it into a corresponding number of 

 segments, each of winch terminated in the marginal spine, those of the last pair being 

 shorter than the preceeding ones. 



Surface of cranidium, hypostoma and pygidium marked by numerous depressed 

 pustules. 



Associated with this species are Blackwelderia tieni, Blackivelderia cilix var. lin- 

 chengensis, Woiiqia triangu.lata, and Teinistion subconica etc. 



Measurements : — 

 Cranidium (cat. 522 a) 



Length of glabella ' 6.3 mm. 



Frontal width oE glabella 3.5 mm. 



Basal wid h of glabella 0.0 mm. 



Width of frontal border 1.3 mm. 



Distance between two spines of the frontal margins 1.0 mm. 



Hypostoma (associated) (cat. 522 b) 



Length ^■^ mm. 



Width 3.0 mm. 



I'ygidium (associated) (cat. 522 c) 



Length 3.3 mm. 



Anterior width 5.0 mm. 



Genus BLACKWELDERIA Walcott 

 Blackwelderia sinensis var linchengensis Sun (var. nov.) 



Plate II, Figs. 6a-d. 



cfr. 1913 Blackwelderia sinensis Walcott, Research in China Vol. ;i, p. 121-123, pi- 9 figs. 5, 5a-g. 



This species is represented by several cranidia, separated free cheeks, one 

 segment of the thorax and an associated pygidium. 



