FORMATIONS AND FOSSILfS OP SOUTH MANCHURIA 91 



kou, 2.5 miles northwest of the Pen-hsi-hu colliery; and also from 

 the same horizon just east of the same colliery, Liao-tung, 

 Manchuria. 



Plesiotypes.—TJ.S.'^M. Nos. 83721 and 83722. 



ABMENOCERAS MAGNITUBULATUM. new species 

 PlATE 19, FlGTJEES 5, 10 



Description. — The holotype, 90 mm long, enlarges from 26.5 mm 

 at the base to 39 mm at a point 39 mm farther up, the apical angle 

 being about 20°. The cross sections of the conch and the siphuncle 

 are circular. The siphuncle is central. Where the diameter of the 

 conch is 29 mm, the concavity of the septa equals 6 mm ; the maxi- 

 mum diameter of the siphuncle here is estimated at 17 mm, and the 

 height of its camerae averages 4 mm; the ratio of the diameter of 

 the siphuncle to that of the conch is 29 : 50. There are 6.5 camarae 

 in a length equal to the diameter of the conch. The inner margin 

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

 slightly downward, the connecting ring beneath each septum meets 

 with this inner margin at an acute angle; a similar acute angle is 

 shown where the immediately overlying connecting ring meets the 

 same septum. The interior of the siphuncle is filled with calcareous 

 matrix, leaving a comparatively narrow endosiphuncular passage 

 and its lateral diverticula. The septa are thickened with the deposi- 

 tion of calcareous matrix, which is deposited only on the anterior 

 sides of the septa in some places, but is found on both sides in others. 

 Living chamber and the surface of the shell unknown. 



Comparisons. — This species may be compared with Armenoceras 

 coulingi (Grabau) amd Armenoceras manchurense (Kobayashi). It 

 is easily distinguished by the larger ratio between the diameter of its 

 siphuncle and that of the conch, and the larger apical angle of the 

 shell. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestone, in the vicinity 

 of Hsiao-nan-kou, 2 miles south of the Niu-hsin-tai colliery, Liao- 

 tung, Manchuria. 



Holotype.— {].^:^M. No. 83723. 



ARMENOCERAS MURAKA.MII (Kobayashi)? 



Plate 19, Figxtees 2-4 



1927. Actinoceras murakamii Kobatshi, Jap. Journ. Geol. and Geogr., vol. 5, 

 no. 4, p. 198, pi. 22, fig. 6. 



Two of my specimens, as is seen in Plate 19, Figures 2-4, seem 

 to agree closely with Kobayashi's Actinoceras Tnurahamii, but un- 

 fortunately I had no opportunity to compare specimens directly, and 



