I'LATK 21 



I'age 

 FiGiiits 1-4. OniKiceras oricntdlc, new species J04 



1, A polished, vertical section through the conch hi a lateral 

 direction, showing the structure of the siphuncle. 



2, Cross section ol' the same specimen sliowiug location and 

 size of siphuncle. 



Miildle Ordovician, Ssuyen lormation: Limestone near Wu- 

 hu-tsui, Liao-tung, Manchuria. 



3, Specimen weathered on its ventral side exposing the 

 siphuncle. 



4, Cross section of the same specimen showing location and 

 size of siphuncle. 



^Middle Ordovician, Ssuyen formation : Limestone near Niu- 

 hsin-tai, Liao-tung, Manchuria. 

 5,6. ArDicnoccras suziikii, new species 98 



5, Specimen weathered on its lateral side exposing the 

 siphuncle. 



6, Cross section of same specimen showing location and size 

 of siphuncle. 



Middle Ordovician, Ssuyen formation : Limestone near I'en- 

 hsi-hu, Liao-tung, Manchuria. 



~. Armcnoccras tani (Grabau) 95) 



A polished, vertical section through the conch in a lateral 

 direction, showing the structure of the sipliuncle. (See 

 also pi. 14, fig. 2, and pi. 40, fig. 3.) 

 Middle Ordovician, Ssuyen formation: Limestone near 

 Ten-hsi-hu, Liao-tung, Manchuria. 

 8,9. AriHcnoccras yabei, new species 100 



8, Specimen weathered on its ventral side, exposing the 

 siphuncle. 



9, Basal segment of same specimen viewed from beneath, 

 showing the location and size of siphuncle. 



Middle Ordovician, Ssuyen formation : Limestone block. 

 Tou-fang-kou, Liao-tung, Manchuria. 



10. Onnoceras chiucnse, new species 102 



A somewhat oblique, polished vortical .section through the 



conch in a lateral direction, showing the structure of 

 the siphuncle. 

 Middle Ordovician. Ssuyen rni-matinn : Liiiu'stnnc near 

 \iu-hsin-tai. Liao-tung. MiMichur:.-!. 



11. Oriiioccras nagaoi, new species 104 



A polished vertical section through the concli iu a lateral 



direction, showing the structure of the si[)liunc]e. (See 

 also pi. 40, fig. 2.) 

 Locality same as Figure 8. 

 128 



