58 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



Surface niimitely punctate under a strong* lens. The largest speci- 

 men of the head has a length of 12 mm. 



The associated p3'g'idlum has a narrow, planulate margin and rather 

 narrow convex axis, marked b}^ live transverse furrows, which divide 

 it into five rings, and a small terminal portion; the furrows extend 

 across the pleural lobes and faintl}' on the margin. The most nearly 

 related form is ^1. alhion. The latter differs in having a proportion- 

 atel}^ shorter frontal limb and rim, and in the form of the glabella. 



Formation and locaUty. — Middle Cambrian, lower central portion 

 of Chang Hsia formation, in limestone interbedded in a green nodular 

 shale; 2 and 2.5 miles south of Yen Chuang, Hsin Tai, Shangtung, 

 China. 



Collected by Eliot Blackwelder, of the Carnegie Institution of 

 Washington Expedition to China. 



Genus ARIONELLUS Barrande. 

 ARIONELLUS AGONIUS, new species. 



Central portion of the head, exclusive of the free cheeks, irregularly 

 sub-quadrilateral, convex. Glabella moderately convex, narrowing 

 slightly toward the front; length and width at the base nearly the 

 same; by reflected light traces of two pairs of glabella furrows may 

 be seen; occipital furrow narrow and shallow; occipital ring nr.rrow 

 at the sides, becoming stronger toward the center, which rises to form 

 the base of a short, strong, backward-sloping spine; dorsal furrow 

 narrow and clearly defined. 



Fixed cheeks narrow and nearly flat at the palpebral lobes; they 

 slope rapidly in front toward the frontal margin, and backward toward 

 the postero-lateral limb; palpebral lobes narrow, about one-third the 

 length of the head; frontal limb narrow directl}' in front of the glabella 

 and rounding over to the rounded frontal rim. 



Surface smooth under a strong lens. The type specimen has a length 

 of 4 mm., with a slightly greater width at the palpebral lobes. 



This species differs from A. alala in having a thickened, rounded 

 frontal rim and a proportionately wider glabella. From A. ajax it 

 differs in being broader and in the presence of an occipital spine. 



Formation and locality. — Middle Cambrian, lower-central portion 

 of the Chang Hsia formation, in thin laj^ers of limestone interbedded 

 in the green shale; Yen Chuang, Hsin Tai, Shangtung, China. 



Collected Ijy Eliot Blackwelder, of the Carnegie Institution of 

 Washington Expedition to China. 



ARIONELLUS AJAX, new species. 



Outline of head, exclusive of free cheeks, sub-rhomboidal, convex. 

 Glabella moderat(dy and uniformly convex, sides converging very^ 

 slightl}' from the base to the rounded front; slight traces of short 



