Plate 20 



Page 



Figure 1. Armenoceras nuclium, new species 94 



A slightly oblique, polished, vertical section in a lateral 

 direction across the conch, showing the structure of the 

 siphuncle. (See also pi. 40, fig. 13.) 

 Middle Ordovician, Ssuyen formation: Limestone block, 

 Niu-hsin-tai, Liao-tung, Manchuria. 



2. Armenoceras species undetermined 101 



A slightly oblique, polished, vertical section in a lateral 

 direction across the conch, showing the structure of the 

 siphuncle. 

 Middle Ordovician, Ssuyen formation : Limestone near Niu- 

 hsin-tai, Liao-tung, Manchuria. 



3, 4. Ormoceras proxinitini, new species 105 



4, Specimen weathered so as to expose the lateral side of the 



siphuncle. 

 3, Transverse section of same specimen at the middle show- 

 , ing the relative size and location of the siphuncle. 

 Middle Ordovician, Ssuyen formation : Limestone near Hsiao- 

 shih, Liao-tung, Manchuria. 



5. Armenoceras sMmizui, new species 97 



A polished, vertical section in a lateral direction across 

 the conch, exposing the structure of the siphuncle. 



Middle Ordovician, Ssuyen formation : Limestone near Tao- 

 yuan-kou, Liao-tung, Manchuria. 



6. Armenoceras penhsiense, new species 95 



A partly polished, natural vertical section in a dorsoventral 

 direction across the conch, showing the structure of the 

 siphuncle. (See also pi. 40, fig. 15.) 

 Middle Ordovician, Ssuyen formation : Limestone near Pen- 

 hsi-hu, Liao-tung, Manchuria. 

 7, 8. Armenoceras sondai, new species 98 



7, Specimen weathered on its ventral side so as to expose 

 the siphuncle. 



Middle Ordovician, Ssuyen formation : Limestone near Hsiao- 

 shih, Liao-tung, Manchuria. 



8, A polished, vertical section in a lateral direction across 

 the conch, exposing somewhat the structure of the 

 siphuncle. (See also pi. 40, fig. 9.) 



Middle Ordovician, Ssuyen formation : Limestone near Tao- 

 yuan-kou, Liao-tung, Manchuria. 

 9. Ormoceras kimurai, new species 102 



A polished vertical section in a lateral direction across the 

 conch, showing the structure of the siphuncle. (See also 

 pi. 40, fig. 1.) 



Middle Ordovician, Ssuyen formation : Limestone near Niu- 

 hsin-tai, Liao-tung, Manchuria. 

 10. Armenoceras rHchthofeni (Freeh) 96 



A slightly oblique, polished vertical section in a lateral direc- 

 tion across the conch, showing the structure of the 

 siphuncle. 



Middle Ordovician, Ssuyen formation : Limestone near Pen- 

 hsi-hu. Liao-tung. Manchuria. 



127 



