66 BULLETIN" 164, UNITED STATES NATIONAL MUSEUM 



equals 22 mm. The rings of the siphuncle are tubular. Interior 

 surface of the siphuncle is slightly thickened by the deposition of 

 calcareous matrix. The interiors of the camerae toward the apical 

 end are filled with calcareous matrix, while the younger part remains 

 empty. The surface of the shell is smooth. 



Comparisons. — This specimen may be compared to Orthoceras 

 chinense Foord, but the larger apical angle, the greater septal dis- 

 tance, and the larger diameter of the conch serve readily in distin- 

 guishing it. 



Formation and locality. — Upper (?) Ordovician: Near Han- 

 chung-fu, Shensi, China. 



Holotype.—V.S.'^.'M. No. 83682. 



ORTHOCERAS LIAOTUNGENSE, new species 

 Plate 13, Figure 6 



Description. — The single specimen collected is 55.5 mm long, en- 

 larging from a diameter of 14 mm at the base to 19.7 mm at the top, 

 the apical angle being 5°. The cross sections of the conch and the 

 siphuncle apparently are circular, but only half of the specimen re- 

 mains, the other half having weathered away. The siphuncle has 

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

 diameter of the conch is three. The concavity of the septa equals 

 7.5 mm. The rings of the siphuncle are approximately tubular or 

 widened but slightly within the camerae. The outer side of the 

 siphuncle and the anterior sides of the septae are moderately thick- 

 ened with the calcareous matrix, having comparatively large spaces 

 in each camerae. The surface of the shell is smooth. 



Comparisons. — The comparatively narrow camerae and the great 

 concavity of the septae serve readily in distinguishing this species 

 from any American or European Orthoceras. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 A black limestone bowlder believed to have come from a part of the 

 Ssuyen formation; in river drift at the Pen-hsi-hu colliery, Liao- 

 tung, Manchuria. 



Eolotype.—V.S.'^.'K. No. 83683. 



ORTHOCERAS RECTISEPTATUM, new species 

 Plate 25, Figure 1 



Although this single specimen is almost too poor to receive a new 

 specific name, characteristic features are well shown. 



Description. — Specimen 31.7 mm long, consisting of about 6 

 camerae, enlarging from 6 mm at the base to 11.7 mm at the top, the 

 apical angle being 11''. The siphuncle is central in position and 1.8 



