1 82 RESEARCH IN CHINA. 



Fixed cheeks narrow and convex; they slope gently backward and merge into 

 the postero-lateral limb, and forward, in advance of the palpebral lobe, slope down- 

 ward to the rounded frontal limb ; palpebral lobes broken away, but from the form 

 of the fixed cheek they appear to have been about one-third the length of the 

 cephalon; postero-lateral limbs about as long as the width of the glabella, and 

 marked by a broad, strong furrow within the narrow postero-lateral margin; frontal 

 limb and rim united to form a rounded, downward-curving frontal border of the 

 cephalon, separated from the glabella by the strong dorsal furrow. 



Surface marked by numerous, irregularly placed pustules, except in the furrows 

 of the glabella, dorsal furrow, and furrow on the postero-lateral limbs. 



The type and only specimen of the cephalon in the collection has a length of 

 17 mm., with the glabella 10 mm. in width and n mm. long. 



In size and general appearance this species may be compared with P. ceto 

 [plate 16, fig. 17]. It differs in its strongly pustulose surface, less convex glabella 

 and fixed cheeks, and in the form of the frontal border of the cephalon. At first 

 sight it is apparently identical with P. calyce [plate 16, fig. 15], but it differs in the 

 form of the transverse furrows and the frontal lobe of the glabella, which in P. 

 calyce is globose, like that of P. ceto. 



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

 the Kiu-lung group [Blackwelder, 19070, 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, Sin-t'ai district, 

 Shan-tung, China. 



Collected by Eliot Blackwelder. 



Ptychaspis cadmus Walcott. 

 Plate 1 6, Figures 19, 190. 



Ptychaspis cadmus WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 70. (Described as a new 

 species essentially as below.) 



This species is represented by more or less fragmentary specimens of the central 

 portions of the cephalon, exclusive of the free cheeks. Glabella moderately convex 

 at the back and strongly convex at the front, marked by a posterior transverse 

 furrow that arches slightly backward, cutting off a narrow lobe between it and the 

 dorsal furrow; anterior lobe a little longer than wide, and marked by a pair of short, 

 narrow furrows opposite the anterior end of the palpebral lobe ; the anterior lobe is 

 convex, but not globose; occipital furrow strong; occipital ring unknown; dorsal 

 furrow strong and rather deep. 



Fixed cheeks very narrow and disappearing into the dorsal furrow in front of 

 the palpebral lobe; posteriorly they slope downward as an irregular ridge to the 

 postero-lateral limb ; palpebral lobes about one-fourth the length of the cephalon and 

 marked by a deep groove within the narrow rim ; frontal limb narrow and sloping 

 outward and downward to the frontal margin from the broad, strong dorsal furrow; it 

 is marked by two transverse rows of large tubercles; postero-lateral limbs unknown. 



The surface of the cephalon, except the furrows, is thickly covered with large 

 pustules. 



A glabella 1 1 mm. in length has a width of 8 mm. ; none of the specimens is suffi- 

 ciently perfect to give measurements for the entire length of the cephalone. 



The species is characterized by the very narrow fixed cheeks and strongly pustu- 

 lose surface. It is associated with P. calchas [plate 16, fig. 13]. 



Formation and Locality. Upper Cambrian: (C41) Lower part of the Ch'au- 

 mi-tien limestone [Blackwelder, 19070, p. 36 (part of the first list of fossils)], 2.7 miles 

 (4.3 km.) southwest of Ch'au-mi-tien, Shan-tung, China. 



Collected by Eliot Blackwelder. 



