108 BULLETIN 16 4, UNITED STATES NATIONAL MUSEUM 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestone, just south of 

 the Wu-hu-tsui colliery, Liao-tung, Manchuria. 



The second specimen (U.S.N.M. No. 83756) (pi. 14, fig. 5; pi. 16, 

 fig. 11), collected in the vicinity of the Pen-hsi-hu colliery, is a mere 

 fragment. It appears to belong to the same species as the foregoing 

 specimen. It is, however, too fragmentary to permit more definite 

 identification. 



Foi^iatlon and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of gray banded limestone beds, near the Pen- 

 hsi-hu colliery, Manchuria. 



A third specimen (U.S.N.M. No. 83757) (pi. 22, fig. 3) is 20 ram 

 long, the cross section of the conch apparently somewhat depressed. 

 The number of camerae in a length equal to the diameter of the 

 conch is 3.5. Where the diameter of the conch is 6 mm that of the 

 siphuncle is 1.2 mm. This specimen appears to belong to another 

 species of Onnocera^., but it is too fragmentary to receive a new 

 specific name. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestones, on the Fu-chin- 

 kou ridge, 2.5 miles southwest of Miyanohara station, Liao-tung, 

 Manchuria. 



The general character of a fourth specimen (U.S.N.M. No. 83758) 

 (pi. 22, fig. 2) agrees closely with that of the third but may be 

 slightly different in having a somewhat larger concavity of the septa. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestones, just south of 

 the Wu-hu-tsui colliery, Liao-tung, Manchuria. 



ORMOCERAS species undetermined 



Plate 22, Figuke 9 



This rather fragmentary specimen (U.S.N.M. No. 83754) is 72 mm 

 long. Its apical angle seems to be very small. The cross sections of 

 the siphuncle and the conch apparently are circular. The siphuncle 

 is central. The number of camerae in a length equal to the lateral 

 diameter of the conch is 3.5. The diameter of the conch at the 

 base is 25 mm and that of siphuncle is estimated as 13.7 mm. 

 Septal distance averages 7.5 mm. The siphuncle is strongly num- 

 muloided, and its interior is filled with calcareous matrix, leaving 

 the central endosiphuncular passage and its lateral diverticula which 

 runs horizontally into the outer sides of the connecting rings. The 

 septal concavity is rather low and its inner margin* is in contact with 

 only the lower side of the preceding segment of the siphuncle. Septal 



