FORMATIONS AND FOSSILS OF SOUTH MANCHURIA 105 



farther up, the apical angle being very low, estimated at 3° or 4°. 

 The ventral side of the conch has been weathered away, so as to 

 expose the septa and the siphuncle. The siphuncle, apparently, was 

 located ventral of the center of the conch. It is estimated that 3.2 

 camerae occupy a length equal to the lateral diameter of the conch. 

 Where this lateral diameter is 12 mm, the concavity of the septa 

 equals 4.5 mm; the maximum diameter of the siphuncle here is 

 estimated at 4.5 mm, and height of its camerae is 3.5 mm on the 

 average. From these dimensions of the siphuncle and camerae it 

 is estimated that the form of the segments of the siphuncle was 

 globular, but somewhat flatter near the anterior margin than the 

 posterior. Septal necks are short. The interior of the siphuncle is 

 occupied by the calcareous matrix, showing very slight traces of an 

 endosiphuncular passage. The septa are thickened irregularly by 

 calcareous matrix, which occurs on both the upper and under sides of 

 the septum, making rather large masses at the mid height of each 

 camera. 



Oom'pmisons. — The general features of this species agree exactly 

 with. Actinocercis suarripanoides^i.TOTa.'To-i^in-go (Tou-fang-kou) and 

 Niu-hsin-tai, described by T. Kobayashi. Both Kobayashi's and 

 my specimens, however, show the characteristic generic features of 

 Ormocerm in having quite narrow and less nummuloid segments of 

 the siphuncle and short septal necks. On the other hand, Grabau's 

 Actinoceras sucrnifunoides (which perhaps belongs to Armenooeras) 

 shows broadly nummuloidal siphuncular segments, and, further, 

 appears to lack entirely traces of the septal necks. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 In the black banded limestone, near the Niu-hsin-tai and the Wu-hu- 

 tsui collieries, Liao-tung, Manchuria. 



Holotype and paratope.— U.S.'NM. Nos. 83749 and 83750. 



ORMOCERAS PROXIMUM, new sp«cies 



Platej 20, FiGUEEs 3, 4 



Description. — The holotype is 41.5 mm long, enlarging very 

 slightly from the base to the top. The cross sections of the conch 

 and siphuncle are apparently circular, but only the lateral side of 

 the conch remains. The siphuncle is very excentric in its position, 

 its center estimated as only 2 mm from the ventral wall of the conch. 

 Three camerae occupy a length equal to the dorsoventral diameter 

 of the conch. Where the dorsoventral diameter is 7.5 mm, the con- 

 cavity of the septa equals 2 mm, and the maximum diameter of the 

 siphuncle here is estimated as 3.9 mm, the height of its camerae 

 averaging 3 mm. The interior of the siphuncle and that of the 

 camerae of the ventral side are densely filled with calcareous matrix. 

 Near the siphuncle the upper side of the septa of the dorsal side 



