DESCRIPTION OF PLATE i. 



Globigerina ? mantoensis Walcott (p. 59). 



I. Exterior view of a bilobed specimen, X 8. From Locality C5, Middle Cambrian, Kiu-lung group, 

 southwest of Yen-chuaug, Shan-tung. U. S. Nat. Mus., Cat. No. 57613. 



Protospongia chloris Walcott (p. 59). 



2 and 20. Spicules showing form and lines of separation of inner and outer portions of rays, X 6. From 

 Locality C 4, Middle Cambrian, Kiu-lung group, southwest of Yen-chuang, Shan-tung. U. S. 

 Nat. Mus., Cat. Nos. 57614 and 57615. 



Coscinocyathus elvira Walcott (p. 60). 



3. Exterior view of a small cup, X 8. U. S. Nat. Mus., Cat. No. 57724- 



3<z. A fragment of cup greatly enlarged to show poriferous outer surface, X 8. U. S. Nat. Mus., Cat. 



No. 57725. 

 36. Oblique section of portion of small cup showing poriferous wall, and cross-sections of walls of cup 



toward apex, X 8. U. S. Nat. Mus., Cat. No. 57726. 

 3C. Enlargement of partly abraded surface where it is divided into slightly irregular squares by 



radiating septa and concentric dissepiments. U. S. Nat. Mus., Cat. No. 57727. 



The specimens illustrated by figs. 3, za-c are from Locality C 75 ; Middle Cambrian, Ki-chou formation, 

 south of Wu-t'ai-hien, Shan-si. 



Protospongia sp. undt. Walcott (p. 60). 



4. Spicule showing the character of the spicule, X 6. From Locality 35 n, Middle Cambrian, Fu-ch6u 



series limestone, Liau-tung, Manchuria. U. S. Nat. Mus., Cat. No. 57728. 



Planolites sp. undt. Walcott (p. 61). 



5. View of specimen described. Natural size. From Locality 36 f, Middle Cambrian, Fu-ch6u series, 



Liau-tung, Manchuria. U. S. Nat. Mus., Cat. No. 57732. 



Micromitra sculptilis (Meek) (p. 61). 



6. Summit and side views of a ventral valve, X 6. U. S. Nat. Mus., Cat. No. 57729. 

 da. Exterior of dorsal valve, X 6. U. S. Nat. Mus., Cat. No. 57730. 



The specimens represented by figs. 6 and da are from Localities 35 n and 35 r, Middle Cambrian, 

 Fu-chou series in limestone, Liau-tung, Manchuria. 



Micromitra (Paterina) lucina Walcott (p. 62). 



7. Summit, side, and back views of a ventral valve, X 6. U. S. Nat. Mus., Cat. No. 57559. 

 70. Exterior of a dorsal valve, X 6. U. S. Nat. Mus., Cat. No. 57731. 



The specimens represented by figs. 7 and 72 are from Locality 35 r. Middle Cambrian, Fu-chou series 

 in limestone, Liau-tung, Manchuria. 



Micromitra (Paterina) labradorica orientalis (Walcott) (p. 62). 



8. Exterior view of type specimen of dorsal valve, X 4. From Locality C 9, Middle Cambrian, Kiu-lung 



group, southwest of Yen-chuang, Shan-tung. U. S. Nat. Mus., Cat. No. 52516. 



Micromitra (Iphidella) pannula maladensis (Walcott) (p. 63). 



9 and 92. Summit view and side outline of a ventral valve, X 6. Locality 35 n, Middle Cambrian, 

 Fu-chou series limestone, Liau-tung, Alanchuria. U. S. Nat. Mus., Cat. No. 57733. 



Micromitra (Iphidella) pannula ophirensis (Walcott) (p. 63). 



10. ioa, and 106. Top, side, and back views of a partly exfoliated ventral valve, X 4. Locality 35 n, 



Middle Cambrian, Fu-chou series in limestone, Liau-tung, Manchuria. U. S. Nat. Mus., 

 Cat. No. 57735. 

 Obolus chinensis (Walcott) (p. 64). 



11. Partly exfoliated, broad form of ventral valve, X 6. U. S. Nat. Mus., Cat. No. 525323. 

 na. Interior of narrow form of ventral valve, X 6. U. S. Nat. Mus., Cat. No. 525326. 



i ib. Partly exfoliated dorsal valve, showing visceral area and central muscle scars (h), X 6. U. S. Nat. 



Mus., Cat. No. 52532^. 

 The specimens illustrated by figures 1 1 , i ici-b are from Locality C fi2. Middle Cambrian, Kiu-lung group, 



argillaceous limestone, south of Yeii-chuang, Shan-tung. 

 nc. Enlargement to 2 diameters of a portion of a slab of limestone on which several ventral and dorsal 



valves of this species occur. [For further illustration see Walcott, 19126, plate xxxix, figs. 



7 a-b.] Locality 35 11, Middle Cambrian, Fu-chou series in limestone, Liau-tuug, Manchuria. 



U. S. Nat. Mus., Cat. No. 57736. 



Obolus obscurus Walcott (p. 66). 



12. Interior of an imperfectly preserved dorsal valve, X 6. U. S. Nat. Mus., Cat. No. 525360. 



iza. Exterior of an exfoliated, partly restored dorsal valve, X 12. U.S.Nat. Mus., Cat. No. 525366. 

 126. Partly exfoliated and broken ventral valve showing concentric and radiating lines on the inner 



layers of the shell, X 4. U. S. Nat. Mus., Cat. No. 525350. 



12C. Enlargement of the concentric stria; of the exterior surface, X 8. U.S.Nat. Mus., Cat. No. 525356. 

 i2d. Exterior surface of a broken dorsal valve, X 6. U. S. Nat. Mus., Cat. No. 525356. 

 Figures 12 and 120 represent specimens from Locality C63, Middle Cambrian, Kiu-lung group, south- 

 west of Yen-chuang, Shan-tung; and i2b-d, specimens from Locality 075, Middle Cambrian, 

 Ki-chou formation, south of Wu-t'ai-hien, Shan-si. 

 Micromitra (Iphidella) pannula White. 



13. Ventral valve, X 3, showing seta; and pedicle, from Locality 35k, Middle Cambrian, Burgess shale 



member of Stephen formation on mountain slope between Mount Field and Mount Wapta, 

 north of Field, British Columbia, Canada. U. S. Nat. Mus., Cat. No. 59801. 



This illustration is inserted in order to give a better conception of the shells illustrated by figs. 9 and 10. 



230 



