DESCRIPTION OF PLATE 16 Continued. 



Ptychaspis calyce Walcott (p. 184). 



IS (X 3, CI>1) and 150 (natural si/i-. ('I:!' Fragments of central parts of cephalou, showing glabdla, 

 occipital ring, and frontal rim; with side outlines of same. Fig. 15 is from Locality ('<>!. the 

 same as fig. 14, Upper Cambrian, Kiu-lung group, southwest of Yen-chuang, Shan-tung. Fig. 

 1511 is from Locality C42, the same as fig. 16, Upper Cambrian, Ch'au-mi-tien limestone, east 

 of Ch'au-mi-tien, Shan-tung. U. S. Nat. Mus., Cat. Nos. 58097 and 58098, respectively. 



Ptychaspis campe Walcott (p. 184). 



1 6. Type specimen, showing portions of central parts of cephalon; and side outline of same, X 4. 



From Locality C42, Upper Cambrian, Ch'au-mi-tien limestone, east of Ch'au-mi-tien, Shan- 

 tung. U. S. Nat. Mus., Cat. No. 58099. 



Ptychaspis ceto Walcott (p. 185). 



17. Type specimen, showing portions of central parts of cephalon. Natural size. From Locality C 38, 



Upper Cambrian, Ch'au-mi-tien limestone at Ch'au-mi-tien, Shan-tung. U. S. Nat. Mus., 

 Cat. No. 58100. 



i-ja. Free cheek, natural size, associated with this species at Locality ('54, Upper Cambrian, Ch'au-mi- 

 tien limestone, west of Tsi-nan, Shan-tung. U. S. Nat. Mus., Cat. No. 58103. 



\-]b. Freecheek, X 3. Associated with specimen represented by fig. 17. (C38.) U.S. Nat. Mus., Cat. 

 No. 58101. 



\TC. Pygidium, X 1.5. Associated with specimens represented by figs. 17 and 17^. (C38.) U.S.Nat. 

 Mus., Cat. No. 58102. 



l^d. Pygidium associated with this species at Locality C 54 [see 170], Upper Cambrian, Ch'au-mi-ti6n 

 limestone, west of Tsi-nan, Shan-tung. U. S. Nat. Mus., Cat. No. 58104. 



Ptychaspis acamus Walcott (p. 179). 



18 and i8a. 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- 

 tien limestone at Ch'au-mi-tien. Shan-tung. U. S. Nat. Mus., Cat. Nos. 58109 and 58110. 



Ptychaspis cadmus Walcott (p. 182). 



I9(X 1.5) and 190 (X 3). Fragmentary specimens of the glabella and palpebral lobes. From Locality 

 C41, Upper Cambrian, Ch'au-mi-tien limestone, southwest of Ch'au-mi-tien, Shan-tung. 

 U. S. Nat. Mus., Cat. Nos. 58111 and 58112. 



