102 BULLETIN 16 4, UNITED STATES NATIONAL MUSEUM 



of the specimen, so that the ratio between the diameter of the si- 

 phimcle and that of the conch can not be determined exactly. Where 

 the diameter of the conch is 23.5 mm, the concavity of the septa is 

 6 mm the length of the camerae 4 mm. The inner margins of the 

 septa are in contact with both the upper and lower connecting rings 

 for only a small radial width. The calcareous deposits in the si- 

 phuncle and camerae are very irregular. 



Formation and locality. — Lower Ordovician, Wuting formation : 

 Black banded limestone, just south of the Wu-hu-tsui colliery, Liao- 

 tung, Manchuria. 



Genus ORMOCERAS Stokes, 1838 



ORMOCERAS CHINENSE, new species 



PiATE 21, Figure 10 



Description. — The holotype is a fairly good specimen 108 mm long 

 and enlarges from a diameter of 32 mm near the base to 37.5 mm 

 at a point 44 mm farther up, the apical angle being estimated at 8°. 

 The cross sections of the conch and siphuncle, apparently, are cir- 

 cular or slightly depressed laterally, but only the ventral half of the 

 conch remains. The siphuncle is central in position. It is estimated 

 that 6.5 camerae occupy a length equal to the diameter of the conch. 

 Where the diameter of the conch is 34.5 mm, the concavity of the 

 septa equals 7.7 mm; the maximum diameter of the siphuncle here 

 is estimated at 6.5 mm ; and the height of its camerae averages 6 mm. 

 From these dimensions of the siphuncle and camerae it is estimated 

 that the form of the segments of the siphuncle was globular, but 

 somewhat depressed vertically at the contacts between successive 

 segments. The interiors of the siphuncle and the camerae are occu- 

 pied by the deposition of the calcareous matrix, leaving a narrow 

 endosipliuncular passage and the narrower diagonal spaces at the 

 middle part of each camera. Living chamber and surface of the 

 shell unknown. 



Comparisons. — I am not acquainted with any American, European, 

 or Oriental species with which this is likely to be confounded. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the dark-gray banded limestone, near Tou- 

 fang-kou, 2.5 miles northwest of Pen-hsi-hu, Liao-tung, Manchuria. 



Holotype.— v. ^.'^.M. No. 83745. 



ORMOCERAS KIMURAI, new species 



Plate 20, Figure 9 ; Plate 40, Figure 1 



Description. — The holotype is 82 mm long, enlarging from a 

 diameter 11 mm near the base to 19 mm at the top. The ventral 



