62 BULLETIN 164, UNITED STATES NATIONAL MUSEUM 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 The lower fossil horizon of the black banded limestones near Hsiao- 

 nan-kou, 2 miles south of the Niu-hsin-tai colliery, Liao-tung; and 

 in the same beds near Shuang-chuan-ssu, 2 miles southwest of 

 Miyanohara station on the Antung-Mukden line, Manchuria. 



Plesiotypes.—X^.^.'^M. Nos. 83674 and 83675. 



CEPHALOPODA 

 Genus ENDOCERAS Hall, 1844 



ENDOCERAS CENTKOTUBULATUM. new species 



Plate 37, Figuees 1-3 



Description. — Specimen 125 mm long, enlarging laterally from 

 29 mm at the base to 42 mm at the top, the apical angle being about 

 8°. The cross sections of the conch and siphuncle are depressed 

 dorsoventrally. Siphuncle is about centrally located. In the cross 

 section of the siphuncle near the top three endocones are found, laid 

 in rows dorsoventrally; 4.5 camerae occupy a length equal to the 

 lateral diameter of the conch. Where the lateral diameter of the 

 conch is 32 mm, the concavity of the septa equals 8.5 mm, and height 

 of its camerae varies from 5.6 to 8.5 mm at the apical part of the 

 specimen. Wlien the septae approach the siphuncle the septal fun- 

 nels become almost cylindrical in form. The lower part of the septal 

 funnels contracts slightly in order to invaginate the septal funnels 

 beneath, the length of this invagination averaging about 3.5 mm. 

 The middle part of the septal funnels does not enlarge so distinctly. 

 The surface of the shell may be smooth so far as determinable 

 from the cast. 



This species is very characteristic in having a central siphuncle 

 and a comparatively septal concavity. 



Formation and locality. — Upper Ordovician. This specimen is 

 believed to have come from a part of lower Ordovician strata; col- 

 lected near Han-chung-fu, Shensi, China, by George D. Louderback. 



Eolotype.—U.^.'^.M. No. 83676. 



Genus CAMEROCERAS Conrad, 1842 



CAMEROCERAS cf. STYLIFORME Grabau 



Plate 81, Figures 2-4 



1922. Cameroceras styliforme Grabau, Ordovician fossils from North China, 

 p. 39, pi. 4, figs. 4-6. 



I collected two fragmental specimens of Cameroceras (U.S.N.M. 

 No. 83677), the general outlines of which are nearly identical with 

 those of Cameroceras styliforme Grabau from the Liangchiashan 



