DESCRIPTION OF PLATE 16—Continued. 
Ptychaspis calyce Walcott (p. 184). 
15 (X 3, C64) and 15a (natural size, C42). Fragments of central parts of cephalon, showing glabella, 
occipital ring, and frontal rim; with side outlines of same. Fig.15 is from Locality C64, the 
same as fig. 14, Upper Cambrian, Kiu-lung group, southwest of Yen-chuang, Shan-tung. Fig. 
15a is from Locality C 42, the same as fig. 16, Upper Cambrian, Ch’au-mi-tién limestone, east 
of Ch’au-mi-tién, Shan-tung. U.S. Nat. Mus., Cat. Nos. 58097 and 58098, respectively. 
Ptychaspis campe Walcott (p. 184). 
16. Type specimen, showing portions of central parts of cephalon; and side outline of same, X 4. 
From Locality C42, Upper Cambrian, Ch’au-mi-tién limestone, east of Ch’au-mi-tién, Shan- 
tung. U.S. Nat. Mus., Cat. No. 58099. 
Ptychaspis ceto Walcott (p. 185). 
17. Type specimen, showing portions of central partsof cephalon. Natural size. From Locality C38, 
Upper Cambrian, Ch’au-mi-tién limestone at Ch’au-mi-tién, Shan-tung. U.S. Nat. Mus., 
Cat. No. 58100. 
17a. Free cheek, natural size, associated with this species at Locality C54, Upper Cambrian, Ch’au-mi- 
tién limestone, west of Tsi-nan, Shan-tung. U.S. Nat. Mus., Cat. No. 58103. 
17). Free cheek, X 3. Associated withspecimen represented by fig.17. (C38.) U.S.Nat. Mus., Cat. 
No. 58101. 
17¢. Pygidium, X 1.5. Associated with specimens represented by figs.17 and 17b. (C388.) U.S. Nat. 
Mus., Cat. No. 58102. 
17d. Pygidium associated with this species at Locality C54 [see 17a], Upper Cambrian, Ch’au-mi-tién 
limestone, west of Tsi-nan, Shan-tung. U.S. Nat. Mus., Cat. No. 58104. 
Ptychaspis acamus Walcott (p. 179). 
18 and 18a. Fragments of the central parts of the cephalon, showing glabella, occipital ring, and narrow 
frontal rim; with side view of fig. 18, X 2. From Locality C45, Upper Cambrian, Ch’au-mi- 
tién limestone at Ch’au-mi-tién, Shan-tung. U.S. Nat. Mus., Cat. Nos. 58109 and 58110. 
Ptychaspis cadmus Walcott (p. 182). 
19 (X 1.5) and 19a (X 3). Fragmentary specimens of the glabella and palpebral lobes. From Locality 
41, Upper Cambrian, Ch’au-mi-tién limestone, southwest of Ch’au-mi-tién, Shan-tung. 
U. S. Nat. Mus., Cat. Nos. 58111 and 58112. 
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