92 BULLETIN 164, UNITED STATES NATIONAL MUSEUM 



Kobayashi's illustrations are too poor to be relied on; consequently 

 I can not be certain that my specimen is the same. To judge from his 

 description, however, it is possible that both represent the same 

 species. 



Description. — One of my best specimens is 32 mm long, enlarging 

 from 10.2 mm near the base to 14 mm at a point 20 mm farther up, 

 the apical angle being 10°. The cross sections of the conch and 

 siphuncle were apparently circular, but only the lateral half of the 

 specimen remains. The siphuncle is very excentric, its center being 

 located 4.5 mm from the ventral wall of the conch ; 4.5 cameras occupy 

 a length equal to the diameter of the conch. Where the diameter of 

 the conch is 13.7 mm, the concavity of the septa is 2.4 mm; height 

 of camerae averages 2.5 mm. Where the lateral diameter of the 

 siphuncle is 5.2 mm, that of the passage of the siphuncle through 

 the septum is 1.5 mm. Between the connecting rings the septum 

 is nearly horizontal. Connecting rings are in contact with the septa 

 both above and below for a radial width of 1 mm. The interior 

 of the siphuncle is filled completely with deposits of calcareous 

 matrix, but that of a second specimen leaves a narrow endosiphuncu- 

 lar passage and its lateral diverticula. The camerae of the ventral 

 side of the shell are nearly filled with the calcareous matrix, while 

 the septa of the dorsal side are thickened very slightly with the 

 deposits of calcareous matrix on the anterior surfaces. 



FoTTRobion and locality. — Middle Ordovician, Ssuyen formation: 

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

 Wu-hu-tsui colliery, and on the Fu-chin-kou ridge, 2.5 miles south- 

 west of Miyanohara station, Liao-tung, Manchuria. 



PZmoi^y^es.— U.S.N.M. Nos. 83724 and 83725. 



ARMENOCERAS NANUM (Grabau) 

 Pirate IS, Figurks 4, 5 



1922. Actinoceras nanum Geabau, Pal. Sinica, ser. B. vol. 1, fasc. 1, p. 87, pi. 7, 



fig. 7 ; pi. 9, fig. 2. 

 1927. Actinoceras nanum Kobayashi, Jap. Journ. Geogr. and Geol., vol. 5, 



no. 4, p. 196, pi. 20, fig. 11 ; pi. 21, fig. 8, pi. 22, fig. 5. 



Description. — A specimen from Niu-hsin-tai (pi. 18, fig. 4), 32.5 

 mm long, enlarges from a lateral diameter of 7.5 mm at its base to 

 11.5 mm near the top, the apical angle being 9°. The cross section 

 of the conch was apparently slightly depressed. The number of 

 camerae in a length equal to the diameter of the conch is eight. 

 Where the diameter of the conch is 11 mm, the concavity of the 

 septa is 2.5 mm, the length of the camera is 1.3 mm, and the maxi- 

 mum diameter of the segments of the siphuncle is 3 mm. The con- 

 necting ring beneath each septum meets the inner margin of the 



