90 BULLETIN 16 4, UNITED STATES NATIONAL MUSEUM 



The specific name is given in honor of Dr. C. Teichert, of Ger- 

 many, from whom I have received many suggestions in connection 

 with this study. 



Comparisons. — The general outline of this species reminds one of 

 Stereoplasmoceras pseudoseptatwni Grabau {ArTnenoceras pseudo- 

 sept atuin) from the Machiakou limestone. North China, but shows 

 a characteristic generic feature of Armenoceras, as seen in the pre- 

 ceding description, and moreover, the comparatively large diameter 

 of its siphuncle serves readily in distinguishing it specifically. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 From a limestone bowlder believed to have come from the Ssuyen 

 formation; river drift at the Niu-hsin-tai colliery, Liao-tung, 

 Manchuria. 



Eolotype.—U.^.'^.M. No. 83720. 



ARMENOCERAS MANCHURENSE (Kobayashi) 



Plate 19, Figubes 6-8 



1927. Actinoceras manchurense Kobayashi, Jap. Journ. Geol. and Geogr., vol. 

 5, no. 4, p. 194, pi. 20, fig. 10 ; pi. 21, fig. 7 ; pi. 22, figs. 2 a-b. 



The better specimen in my collections is 61 mm long, enlarging 

 from a lateral diameter of 16.5 mm at its base to 31 mm at a point 

 49 mm farther up, the apical angle being 15°. The cross section of 

 the conch, apparently, was depressed, while that of the siphuncle 

 was probably circular. The number of camerae in a length equal to 

 the lateral diameter of the conch is 10. Septa regularly concave, the 

 concavity averaging 6 mm. The siphuncle is strongly annulated: 

 where the diameter of the conch is 28.5 mm, the maximum diameter 

 of the segment of the siphuncle is 12.5 mm. The inner margin of 

 the septa, at the passage of the siphuncle through it, curves very 

 slightly downward, but does not form a septal neck. Septal rings 

 are in contact with the septa both above and below for a radial 

 width of 2 mm. This feature between the connecting rings and 

 septa is very characteristic of Armenoceras. The inner margin of 

 the siphuncle and the anterior surface of the septa are covered with 

 calcareous deposits. The distance between the siphuncle and the 

 ventral side of the conch is 3 mm at the base and near the top, 

 but the siphuncle is excentric near the top while it is found rather 

 centrally located at the base. 



A second specimen (pi. 19, fig. 8) from near the Pen-hsi-hu col- 

 liery is 70 mm long, its cross section being somewhat crushed laterally 

 and dorsoventrally. The siphuncle is very excentric in location, 10 

 camerae occupying a length equal to the lateral diameter of the 

 conch. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestone, near Tou-f ang- 



