FORMATIONS AND FOSSILS OF SOUTH MANCHTJIIIA 71 



trast to the latter, which shows many nummuloidal segments of the 

 siphuncle. 



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

 In the lower fossil horizon of the black banded limestone just north of 

 the Pen-hsi-hu colliery, Liao-tung, Manchuria. 



Holotype.—V.S.'^M. No. 83691. 



CYCLOCERAS (?) MARGINALE, new species 



Plate 27, Figtjee 5; Piate 40, Figuee 11 



Description. — This single specimen is 105 mm long, enlarging dor- 

 soventrally from a diameter of 18 mm at the base to 26 mm at a 

 point 71 mm farther up; the apical angle is comparatively low. 

 The cross section of the conch is slightly compressed. The siphuncle 

 is excentric in position, its center located 8 mm from the ventral wall 

 of the conch. The number of camerae in a length equal to the 

 diameter of the conch is eight. The surface of the conch is fairly an- 

 nulated, and five of these annulations occupy a length equal to 

 the diameter of the conch. When the diameter of the conch is 26 

 mm, the concavity of the septa is 5.5 mm; the maximum diameter 

 of the siphuncle here is estimated at 4.5 mm, and the height of its 

 camerae averages 3.2 mm. The inner margins of the septa form a 

 short septal neck. These inner margins are in contact with only 

 the lower sides of the preceding connecting rings. The interior of 

 the siphuncle has no trace of the deposition of calcareous matrix. 

 The camerae of the older part of the shell are densely filled with the 

 calcareous matrix, which becomes gradually less toward the younger 

 part. Since the surface of the shell of this species is not exposed, I 

 can not decide exactly whether it belongs to Spyroceras or Gy- 

 cloceras^ and therefore it is tentatively assigned to Cycloceras. 



Comparisons. — Comparatively large shell, the larger septal con- 

 cavity, the form of the segments of the siphuncle and excentric posi- 

 tion of the siphuncle serve to differentiate this species from others 

 found in the Ordovician beds of the Orient. I am not acquainted 

 with any American or European species with which this one is 

 likely to be confounded. 



Formation and locality. — ^Lower Ordovician. Wuting formation : 

 In the black banded limestone beds, near the second tunnel, 1 mile 

 north of Pen-hsi-hu, Liao-tung, Manchuria. 



Eolotype.—JJ.S.'^.'M. No. 83692. 



CYCLOCERAS (?) SHENSIENSE, new species 



Plate 37, Figuees 4, 5 ; Plate 38, FigukeJ 4 



Description. — Louderback's collection contains another specimen, 

 50 mm long, that enlarges slightly from the base to the top. The 



