I So RESEARCH IN CHINA. 



The surface is marked by strong, scattered pustules over the glabella; little 

 trace of them on the fixed cheeks and frontal rim. The two specimens of the 

 cephalon of this species in the collection vary somewhat in the form of the frontal 

 rim, it being nearly flat in one and slightly concave in the other. 



The most nearly related form is Ptychaspis brizo [p. 181]. 



Formation and Locality. Upper Cambrian: (C64) Upper limestone member of 

 the Kiu-lung group [Blackwelder, 190712, pp. 37 and 42 (first list of fossils), and fig. 

 10 (bed 20), p. 38], 2.7 miles (4.3 km.) southwest of Yen-chuang, and (C61) a dense 

 black limestone in the uppermost limestone member of the Kiu-lung group [idem, 

 pp. 37 and 41 (third list of fossils), and fig. 10 (bed 13), p. 38], 3 miles (4.8 km.) 

 southwest of Yen-chuang, Sin-t'ai district, Shan-tung, China. 



Collected by Eliot Blackwelder and Li San. 



Ptychaspis bella Walcott. 

 Plate 17, Figure 9. 



Ptychaspis bella WALCOTT, 1906, Proc. U. S. Nat. Mus., vol. xxx, p. 585. (Described as a. new species 

 essentially as below.) 



This species is represented by a single specimen of the central portions of the 

 cephalon, exclusive of the postero-lateral limbs and free cheeks. Glabella subrec- 

 tangular in outline, moderately convex, and crossed by a backward-arching furrow 

 which separates a narrow segment from the large anterior lobe, which has a length 

 of 6.6 mm. and a width at the center of 5 mm. ; the anterior lobe of the glabella is 

 marked close to the dorsal furrow by very short furrows which indicate the second 

 pair of glabellar furrows ; the posterior transverse furrow is rather broad and deep 

 at the sides, becoming somewhat shallower at the center; the posterior segment has 

 a uniform width across the central portions, widening out at the ends in front; 

 occipital furrow transversely rounded and rather deep; occipital ring transverse, 

 slightly convex, and about the same width as the posterior segment of the glabella; 

 dorsal furrow deep and strong at the sides and in front of the glabella. 



Fixed cheeks narrow and rising abruptly from the dorsal furrow, nearly flat 

 opposite the palpebral lobes; they slope abruptly downward toward the posterior 

 furrow and toward the frontal rim ; palpebral lobes narrow, rounded, and separated 

 from the fixed cheeks by strong, narrow furrows; frontal rim convex, prominent, 

 and separated from the glabella by the deep dorsal furrow and from the fixed cheeks 

 by a narrow, deep furrow that extends obliquely outward and forward from opposite 

 each antero-lateral angle of the glabella. 



The surface of the glabella is marked by raised, irregular, more or less inoscu- 

 lating, sharp ridges, the general direction of which is transverse to the axis of the 

 glabella ; the fixed cheeks are marked by ridges somewhat like those on the glabella, 

 which are subparallel to the dorsal furrow and the furrow within the palpebral lobes ; 

 the ridges on the frontal limb are broken up into large granulations by the inoscu- 

 lating furrows. A cephalon 1 1 mm. in length has a width of 12 mm. at the palpebral 

 lobes. 



The general form of the central parts of the cephalon of this species suggests 

 Ptychaspis acanms [p. 179]. It differs from the latter in the form of the glabella in 

 front of the transverse glabellar furrow, the elevated lines on the fixed cheeks instead 

 of granulations, and in minor details of the occipital and glabellar furrows. 



Formation and Locality. Upper Cambrian: (074) A dense blue dolomitic lime- 

 stone at the top of the Ki-chou limestones [Willis and Blackwelder, 1907, pp. 139 

 and 145 (fifth list of fossils)], 4 miles (6.4 km.) east of Fang-lan-chon, Shan-si, China. 



Collected by Eliot Blackwelder. 



