72 BULLETIN 16 4, UNITED STATES NATIONAL MUSEUM 



cross sections of the conch and siphuncle apparently were originally 

 circular, but have been more or less compressed laterally by pressure. 

 The siphuncle is located somewhat ventrally. About six annula- 

 tions occur in a length equal to the diameter of the conch. The 

 number of camerae in an equal length is 7.2. Where the lateral 

 diameter of the conch is 22.2 mm, the concavity of the septa equals 

 4.6 mm, and the height of its camerae averages 3.2 mm. The 

 siphuncle is tubular and does not enlarge within the camerae. The 

 septal neck is very short, about 0.6 mm or less in length. The annu- 

 lations are rather indistinct, are 4 mm apart from crest to crest, 

 and run obliquely along the lateral sides of the specimen. 



Since the surface of the shell of this specimen is not preserved, 

 I can not decide definitely whether it belongs to Spyroceras or to 

 Cycloceras^ and it is therefore assigned tentatively to Cycloceras. 



Comparisons. — In general this species may be compared with 

 Cycloceras {?) 77ianchuriense, but differs in having the tubular 

 siphuncle, indistinct annulations, and a comparatively large number 

 of annulations in a length equal to the diameter of the conch. 



Formation and locality. — Upper Ordovician: Near Han-chung- 

 fu, Shensi, China. 



Eolotyjje.—V. S.'N.M. No. 83693. 



CYCLOCERAS (?) PEITOUTZENSE Grabau 



Plate 14, FiGtrKE& 3, 4 



1922. Cycloceras (?) peitoutzense Grabau, Pal. Sinica, ser. B, vol. 1, fasc. 1, 



p. 63, pi. 6, fig. 2 (not. pi. 6, figs. 1, 3, 4). 

 1927. Cycloceras (?) peitoutzense Kobayashi, Jap. Journ. Geol. and Geogr., 



vol. 5, no. 4, p. 184, pi. 21, fig. 1. 



It is quite likely that two or three species belonging to Cycloceras 

 and Spyroceras are included in Grabau's Cycloceras (?) peitoutzense^ 

 because, according to his description, the shells of his second to fifth 

 specimens have fine concentric striae between the interspaces of the 

 annulations; his first specimen, on the contrary (pi. 6, fig. 1), has 

 very faint longitudinal lines upon the early portion of the fragment. 

 Therefore, it is clear that the four specimens with concentric striae 

 belong to Cycloceras but that the other specimen belongs to Spyro- 

 ceras. Morever, I have some doubt whether his second (pi. 6, fig. 2), 

 third, fourth (pi. 6, fig. 3), and fifth (pi. 6, fig. 4) specimens are the 

 same species. Two of my specimens are also too incomplete to 

 settle the question whether they belong to Cycloceras or Spyroceras. 

 It seems to me, however, that my specimens may coincide with Gra- 

 bau's second specimen, so I am describing them tentatively as a 

 species of Cycloceras (?). 



Since Grabau's first specimen may belong to Spyroceras^ I shall 

 designate his second specimen as the lectotype of Cycloceras (?) 



