DESCRIPTION OF PLATE 23. 
Asaphiscus iddingsi Walcott (p. 221). ; 
1. Dorsal shield, flattened in argillaceous shale, X 2. From Locality 36e, Middle Cambrian, Fu-chéu 
series, shale interbedded in limestone, Liau-tung, Manchuria. U.S. Nat. Mus., Cat. No. 
57586. 
1a. Cranidium, X 2, from limestone associated with the shale mentioned under fig. 1. (35r.) U.S. 
Nat. Mus., Cat. No. 58269. 
1b. A smaller cranidium, X 3, associated with the specimen represented by fig. ra. U.S. Nat. Mus., 
Cat. No. 58270. 
Bathyuriscus manchuriensis Walcott (p. 219). 
2. Fragment of shale with three cranidia flattened in it, X 3. U.S. Nat. Mus., Cat. No. 57587. 
2a. Associated free cheek, X 3. U.S. Nat. Mus., Cat. No. 58271. 
2b. Associated thoracic segment, X 3. U.S. Nat. Mus., Cat. No. 58272. 
2c. Associated pygidium, X 3. U.S. Nat. Mus., Cat. No. 58273. 
2d. Associated minute cranidium, X 8. On shale with specimens represented by fig. 2. U.S. Nat. 
Mus., Cat. No. 57587. 
2e and 2f. Associated hypostomas, X 4. U.S. Nat. Mus., Cat. Nos. 58275 and 58276. 
All of the specimens illustrated are from Locality 86h, Middle Cambrian, Fu-chou series, argillaceous, 
shales, Liau-tung, Manchuria. 
Illenurus canens Walcott (p. 222). ; 
3. Cranidium from Locality C54, Upper Cambrian, Ch’au-mi-tién limestone, two-thirds of a mile (1.1 
km.) west of Tsi-nan, Shan-tung. U.S. Nat. Mus., Cat. No. 58279. 
3a. Cranidium, X 2, from Locality C42, Upper Cambrian, Ch’au-mi-tién limestone, 7.5 miles (12 km.) 
east of Ch’au-mi-tién, Shan-tung. U.S. Nat. Mus., Cat. No. 58281. 
3b. Pygidium (natural size) associated with specimen represented by fig. 3. From Locality C54. U.S. 
Nat. Mus., Cat. No. 58280. 
3c. Pygidium from Locality C38, Upper Cambrian, Ch’au-mi-tién limestone at Ch’au-mi-tien, Shan- 
tung. U.S. Nat. Mus., Cat. No. 58282. 
Illenurus ceres Walcott (p. 223). 
4. Dorsal view and side outline of type specimen of cranidium, X 1.5, from Locality C38, Upper Cam- 
brian,Ch’au-mi-tién limestone at Ch’au-mi-tién, Shan-tung. U.S. Nat. Mus., Cat. No. 58285. 
4a. Pygidium associated with the specimen represented by fig. 4. U.S. Nat. Mus., Cat. No. 58286. 
Illenurus dictys Walcott (p. 224). 
5. Dorsal view and side outline of type specimen of cranidium, X 4. From Locality C56, Upper 
Cambrian, Ch’au-mi-tién limestone, west of Tsi-nan, Shan-tung. U.S. Nat. Mus., Cat. 
No. 58287. 
5a. Pygidium associated with the specimen represented by fig. 5, X 3. U.S. Nat. Mus., Cat. No. 
58288. 
Illenurus sp. undt. Walcott (p. 222). 
6. Large pygidium (natural size) from Locality C54, Upper Cambrian, Ch’au-mi-tién limestone, two- 
thirds of a mile (1.1 km.) west of Tsi-nan, Shan-tung. U.S. Nat. Mus., Cat. No. 58289. 
Gen. and sp. undt. (a) Walcott (p. 224). 
7. Pygidium of unknown generic and specific relations, X 4. From Locality C9, Middle Cambrian, 
Kiu-lung group, southwest of Yen-chuang, Sin-t’ai district, Shan-tung. U.S. Nat. Mus., 
Cat. No. 58290. 
Gen. and sp. undt. (b) Walcott (p. 224). 
8. Small pygidium of unknown generic and specific relations from Locality C67, Upper Cambrian, a 
piece of limestone in the drift, one-third of a mile (0.5 km.) west of the west city gate, Tsi-nan, 
Shan-tung. U.S. Nat. Mus., Cat. No. 58291. 
Hysterolenus ? sp. undt. Walcott [see plate 22, figs. 9, 9a] (p. 219). 
9. A beautifully ornamented pygidium of unknown specific relations, from Locality C64, Upper Cam- 
brian, Ch’au-mi-tién limestone, 2.7 miles (4.3 km.) southwest ofYen-chuang, Shan-tung. U.S. 
Nat. Mus., Cat. No. 58268. 
Aluta bergeroni (Walcott) (p. 225). 
10. A minute left valve, greatly enlarged. (C32.) U.S. Nat. Mus., Cat. No. 56493. 
Aluta enyo (Walcott) (p. 225). 
11. A left valve, greatly enlarged, showing position of ocular tubercle and form of valve. (C82.) 
U.S. Nat. Mus., Cat. No. 56497. 
Aluta eris (Walcott) (p. 226). 
12. A fragmentary right valve, with outline restored to show the supposed form. (C32.) U.S. Nat. 
Mus., Cat. No. 56496. 
Aluta fragilis (Walcott) (p. 226). _ 
13. A right valve, illustrating manner in which the thin test is crushed by compression. (0382.) 
U.S. Nat. Mus., Cat. No. 56495. 
Aluta sterope (Walcott) (p. 227). 
14. Right valve, showing the peculiar markings upon the surface. (C32.) U.S.Nat.Mus., Cat. No. 
56498. 
Aluta woodi (Walcott) (p. 227). 
15. Left valve, showing ocular tubercle, and looped ridge extending from near anterior angle to center 
of valve. (C32.) U.S. Nat. Mus., Cat. No. 56494. 
All of the specimens represented by figs 10-15 are from Locality C32, Middle Cambrian, river drift 
south of Chén-p’ing-hién, Shan-si. 
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