POBMATIONS AND FOSSILS OF SOUTH MAN-GHUBIA 75 



farther up, the apical angle being 9°. The cross sections of the conch 

 and the siphuncle are apparently circular, but only the lateral half 

 of the shell remains, the other half being weathered away. The 

 number of camerae in a length equal to the diameter of the conch 

 is about 4.5. Septa regularly concave ; their concavity is not so con- 

 spicuous, and is rather shallow, being 4.5 mm in depth. The si- 

 phuncle is excentric, its center located 10.5 mm from the ventral side 

 of the conch at a point near the top. Where the diameter of the 

 conch is 27.5 mm, and where the septa are 6 mm apart, one of the 

 segments of the siphuncle has a maximum diameter of 5 mm at 

 mid height, constricting to 2.5 mm at its passage through the septum. 

 The resultant form of segments of the siphuncle is almost globular, 

 slightly depressed anteriorly. Almost all the interior of the camerae 

 is filled with calcareous deposits, leaving very narrow strips here 

 and there, while the inner side of the siphuncle is empty except for 

 a slight deposit just inside its passage through the septum. 



The specific name is given in honor of T. Kobayashi, of the Tokyo 

 Imperial University in Japan. 



Gomparisons. — This species may be closely allied to Sactoceras 

 decipiens (Barrande), and Sactoceras impTohus (Barrande) from 

 stage E, Bohemia, but the shallower concavity of the septa serves 

 readily in distinguishing it. 



Formation and locality. — ^Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestone beds near Pen- 

 hsi-hu, Liao-tung, Manchuria. 



Eolotype.—{].^:^M. No. 83697. 



SACTOCERAS NIUHSINENSE, new species 



Plate 14, Figuee 13 ; Plate 40 ; Figttee 18 



Description. — The holotype is 74 mm long, enlarging very slightly 

 from base to top. The cross sections of the conch and siphuncle 

 apparently are circular, but only the ventral half of the conch re- 

 mains, the dorsal half being weathered away. The siphuncle is cen- 

 trally located. The number of camerae in a length equal to the 

 diameter of conch is about 10. Where the diameter of the specimen 

 is 37.5 mm and where the septa are 3.5 mm apart, one of the segments 

 of the siphuncle has a maximum diameter of 5 mm at mid height, 

 constricting to 2.6 mm at its passage through the septum. The re- 

 sultant form of the siphuncle segments is somewhat depressed glob- 

 ular. The average concavity of the septa is 6.5 mm. The interior 

 of the siphuncle and the conch are almost empty, but a very small 

 quantity of the lunate calcareous matrix is found on the interior of 

 the siphuncle at its passage through the septa; also the septa are 

 thickened slightly here and there by deposits of calcareous matrix. 



