FORMATIONS AND FOSSILS OF SOUTH MANCHUEIA 101 



ARMENOCERAS species undetermined 



Plate 19, Figukb 9; Plate 20, Figure 2 



Description. — First specimen (U.S.N.M. 83740) 29 mm long, en- 

 larges at an apical angle of about 11° from a lateral diameter of 9.5 

 mm at its base to 12.5 mm at a point 13 mm farther up. It is esti- 

 mated that six camerae occur in a length equal to the lateral diameter 

 of the conch. The cross sections of the conch and the siphuncle, ap- 

 parently, are circular, but only the ventral half remains. The si- 

 phuncle is located at the center of the conch. Where the diameter of 

 the conch is 13 mm the concavity of the septa is 3 mm, the length of 

 the camerae 2.5 mm, and the maximum diameter of the segments of 

 the siphuncle 3.2 mm. The inner margins of the septa are connected 

 with both upper and lower connecting rings at very acute angles. 

 The interior of the siphuncle is almost entirely filled with calcareous 

 matrix. The calcareous deposit in the camerae is irregular. 



A second specimen (U.S.N.M. 83741) from Niu-hsin-tai (pi. 20, 

 fig. 2) appears to have a somewhat excentric siphuncle, but other- 

 wise agrees quite closely with the first. 



CoTTi'parisons. — These specimens may be compared with Arme- 

 noceras narmm (Grabau), but the longer septical distance, compara- 

 tively larger siphuncle, and the larger apical angle of the conch 

 serve readily in distinguishing this species. Therefore, these speci- 

 mens may probably belong to a new species, but are too fragmentary 

 to receive a specific name. 



Formation and localities. — Middle Ordovician, Ssuyen formation : 

 From both upper and lower fossil horizons of the black banded 

 limestone beds, near the Niu-hsin-tai colliery and on the Fu-chin- 

 kou ridge, southwest of Miyanohara station, Liao-tung, Manchuria. 



ARMENOCERAS species undetermined 



Plate 25, Figitee 2 



I also collected a fragmentary specimen of Armenoceras (U.S.N.M. 

 83744) from the Wuting formation, near the Wu-hu-tsui colliery. 

 As this is one of the rare specimens of Armenoceras from the Wuting 

 formation in Manchuria, it is described despite its imperfect 

 condition. 



Description. — The specimen is 32 mm long, enlarging laterally 

 at an apical angle of about 8° from a lateral diameter of 18.5 mm 

 at the base to 24 mm at its top. About six camerae occupy a length 

 equal to the lateral diameter of the conch. The cross section ap- 

 parently is elliptical laterally. The siphuncle is located somewhat 

 ventrally. As a small fault runs through the center of the siphuncle, 

 the septa and segments of siphuncle are somewhat displaced 

 vertically between the lateral sides of the longitudinal medial line 



