88 BULLETIN 164, UNITED STATES NATIONAL MUSEUM 



conch is 18 mm, the concavity of the septa is 3 mm, the length of the 

 camerae is 2,5 mm, and the maximum diameter of the segments of the 

 siphuncle is 9.5 mm. The inner margin of the septa, at the passage 

 of the siphuncle through it, curves slightly downward. The over- 

 lying cormecting rings are adnate to the intermediate septa for a 

 short space in the area immediately surrounding the passage of the 

 siphuncle through the septa, while the underlying connecting rings 

 meet the inner margin of each septum at acute angles. The deposi- 

 tion of calcareous material in the camerae is rather pronounced in 

 the earlier part of the shell but becomes less in the later. For the 

 most part it is added to the anterior portion of the septa, but in some 

 cases appears slightly on their posterior surfaces. The septa are 

 sometimes undulating. The siphuncle, evidently, was located ven- 

 trally. Living chamber and the surface of the shell are unknown. 



The specific name is given in honor of Prof. I. Hayasaka, of the 

 Taihoku Imperial University in Japan. 



Coviparisons. — The general form of this species is rather like 

 Armenoceras {Actinoceras) tani (Grabau), but the comparatively 

 large diameter of the siphuncle, the deeper concavity of the septa, 

 the rather undulating septa, and the smaller apical angle of the conch 

 serve readily to distinguish it. 



Formation and locality. — Middle Ordovicion, Ssuyen formation: 

 A grayish black limestone bowlder believed to have come from the 

 Ssuyen formation, river drift at the Niu-hsin-tai colliery; another 

 f ragmental specimen comes from the lower f ossij horizon of the black 

 banded limestone 5 miles west of Chiao-tou station, Liao-tung, Man- 

 churia. 



Holotype and paratype.—U.S.'^M. Nos. 83717 and 83718. 



ARMENOCERAS KmOI, new species 



Plate 18, Figuee 9 ; Plate 40", Figure 5 



Descriftion. — The holotj^pe is 88 mm long, enlarging from a 

 diameter of 26 mm near the base to 29 mm at a point 48 mm farther 

 up. The cross section of the conch was apparently somewhat de- 

 pressed, while that of the siphuncle was circular. The siphuncle 

 is located in the center of the conch. The number of camerae in 

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

 diameter of the conch is 27 mm, the concavity of the septa is 7 mm 

 and the length of the camerae 3.5 mm. Where the lateral diameter 

 of the siphuncle is 10 mm, that of the passage of the siphuncle 

 through the septum is 4.5 mm. Between the connecting rings this 

 septum is more nearly horizontal and its inner margin directed 

 slightly downward. This inner margin extends about 3 mm inward 

 from the ventral projection of the outer margin of the septal rings. 



