N0.1415. CAMBRIAN FAUNAS OF CHINA— WALCOTT. 23 



The glabella is formed of a po.sterior, .slightly convex lobe that is 

 little more than one-fourth the width of the head and less than one- 

 half its length; it is marked a little in advance of its center by a small, 

 pointed tubercle; in front of the posterior lo]>e there is a faintly out- 

 lined conical extension of the glabella that ditiers more or less in form 

 and strength in nearly every specimen of the head; it is usually very 

 obscure; lateral lobes moderately convex and uniting in the front 

 without interruption in the convexity or surface. 



The thoracic segments associated with the cephalic and caudal shields 

 have a convex axial lobe with narrow pleural lobes; the axial lobe is 

 divided into a central portion and two lateral portions by narrow fur- 

 rows, giving the effect of two large oval tubercles between the dorsal 

 furrow and the central portion of the segment; the short pleural lobe 

 is marked by a very narrow pleural furrow a short distance back of 

 its center. 



The caudal shield associated with the cephalic shield is slightl}- 

 shorter in proportion to its width and less convex; it is bordered by a 

 flat, rather broad rim, that is narrow at the front margin, gradually 

 increasing to its greatest width l)ehind, where its inner margin curves 

 inward to form a blunt angle at the point opposite the axial lobe; the 

 front niargin is narrow and elevated in front of the lateral lobes 

 and bordered with a narrow, slightly convex, sharply detini^d axial 

 segment. 



Axial lobe about one-third the entire width, moderately convex, 

 and marked on its anterior third l\y an elongate, slightly elevated 

 tiU>ercle from which on some specimens, but not on others, two very 

 faint grooves extend outward and then curve obliquel}" backward to 

 the dorsal furrow, the front groove being opposite the apex of thc^ 

 tul)ercle; in some examples the axial lobe contracts opposite the cen- 

 tral tubercle and expands at the frontal margin, where an oblique, 

 very faintly defined furrow outlines a small oval lobe; dorsal furrow 

 narrow and sharply detined all al)out the central axis; back of the axis 

 it unites and passes back into the furrow within the border; lateral 

 lobes gently convex, usually about the width of the axial lobe near 

 the central portions, narrowing posteriori}^, and d3nng out at the 

 short, shallow furrow at the posterior point of the axial lobe. 



Surface of cephalic and caudal shields and thoracic segments mi- 

 nutely punctate. 



This species differs from Agnostus chinensis Dames, which occurs 

 abundantly in the Chang Hsia formation, in having a short glabella and 

 broader lateral lobes on the cephalic shield, and broader lateral lobes 

 and flat border on the pygidium. It is of the type of and very closely 

 related to A. 'parcifrons Linnarsson, from which it differs in the pro- 

 portion of the glabella to the length of the cephalic shield and in the 

 flatter margins of the cephalic and caudal shields. 



