98 BULLETIN 164, UNITED STATES NATIONAL MUSEUM 



ARMENOCERAS SONDAI, new species 



Plate 20, Figures 7, 8 ; Plate 40, Figure 9 



Description. — Holotype is 65 mm long, slightly enlarged laterally 

 from the base to the top. The cross section of the conch was appar- 

 ently laterally depressed, but the dorsal half is weathered away. 

 The center of siphuncle is located 6 mm from the ventral wall of the 

 conch. There are about seven camerae in a length equal to the 

 diameter of the conch. "^Vliere the diameter of the conch is 3*2 mm, 

 the concavity of the septa equals 5.5 mm; the maximum diameter 

 of the siphuncle here is estimated as 8.5 mm, and height of its 

 camerae averages 4.7 mm; thus the segments of siphuncle are 

 strongly vertical both above and below. Between the segments 

 of the siphuncle, the inner margin of the septa may be in contact 

 with both the upper and lower connecting rings for some radial dis- 

 tance. In the interior of the siphuncle and on the anterior side of 

 the septa some deposition of calcareous matrix is found. 



Though this specimen is fragmentary, the comparatively smaller 

 ratio between the diameter of the siphuncle and that of the conch, 

 lesser enlargement laterally of the conch from the base to the top, 

 and the manner of deposition of the calcareous matrix in the camerae 

 are characteristic features. 



The specific name is given in honor of T. Sonda, who collected 

 the specimen. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Lower fossil horizon of the black banded limestone, near the Tao- 

 yuan-kou colliery, Liao-tung, Manchuria. A fragmental second 

 specimen found in the same horizon, near the Hsiao-shih colliery, 

 Manchuria. 



Holotype and pofratype.—U.^.'EM. Nos. 83734 and 73735. 



ARMENOCERAS SUZUKII, new species 



Plate 21, Figures 5, 6 



DescHption. — A single good specimen 73.5 mm long becomes the 

 holotype of another new species enlarging from 13.5 mm near the 

 base to 20 mm at a point 60 mm farther up, the apical angle being 

 very small. The cross sections of the conch and the siphuncle appar- 

 ently are circular, but only the lateral half of the specimen remains. 

 The siphuncle is very excentric, its center being located 6.5 mm from 

 the ventral wall of the conch. Where the diameter of the conch is 

 19 mm, the concavity of the septa equals 4.5 mm ; the maximum of the 

 sii)huncle here is estimated as 7.5 mm, and the height of its camerae 

 averages 2.5 mm. There are 7.5 camerae in a length equal to the 

 diameter of the conch. Between the connecting rings each septum 



