Vol. I. C. C. Yii — Ordovician Cephalopoda of Central China (ii) 51 



the preceding ones, which is a common case occurring in the conchs of cephalopods. 

 Septa moderately concave, having a depth nearly equivalent to one fourth the maximum 

 width of the shell. 



Siphuncle narrow, lying in the central part with a circular cross section. Its size 

 is about 1/9 the diameter of the shell at the lower end, and i/n at the upper. The 

 septal necks extend scarcely longer than 1/3 the septal interspace. The camerat; are 

 mainly filled with crystalline calcite, though some are also filled with the material in 

 which the specimen is embedded. 



One specimen of a different individual (PI. VIII., Fig. 4.) represents a young shell 

 of smaller size. The septate portion has a length of 68 mm. excluding the living cham- 

 ber, which is very large or more than 3 times the diameter at its base or nearly about 1/2 

 the total length of the fragment. Rate of tapering i in 7.5. The septa are equally 

 separated, being 7 mm. in distance, while the diameter of the conch meas^ires 13 mm. at 

 the lower end and 19 mm. at the upper. Siphuncle narrow, central, cylindrical, preserv- 

 ed oiily in the smaller extremity of the naturally sectioned specimen. It is about 1/9 the 

 diameter in size. 



The third specimen (PI. IX., Fig. i) collected from Tung-chiao-cheng, attains a 

 length of 132 mm. and expands its shell at the rate of i in 7, It terminates in a blunt 

 end at an apical angle of 15°. Shell slightlj^ curved, which may be regarded as 

 accidental. Cross section subcircular (probably by compression). Near the apical por- 

 tion the septal distances gradually increase from 5 mm. to 10 mm., where the shell has the 

 corresponding longer diameter of 9 and 19 mm. Above this stage the septa are" 12 mm. 

 distant from each other. Still higher up they have been crushed, but from what 

 remains we know that they are also equidistant at an interval of about 12 mm. throughout 

 the upper portion, where the shell enlarges its diameter from 22-27 mm. 



Comparison: This form has some affinities with the Orthoceras epulatis Bar- 

 rande' , but the septa in the latter form are much closer together and the 

 septal necks much shorter. It is similar to Orthoceras chinense Foord except 

 for the shorter septal necks and the equal septal distances, the last feature also serving 

 to distinguish it from the other varieties of Foord's species mentioned above. 



Horizon and Looaf.itiks: The specimens (PI. VIII., Figs. 3-4) were found in the 

 beds overlying the thick blue Hmestone and underlying the red bed near Pei-hua-pu, 

 Pu-chi-hsien (C. Li and W. P. Shu). The last one described (PI. IX., Fig. i) is 

 abundant in the upper Neichiashan formation at Mei-hua-ling (t^ :[£ '4k.) 12 li east of Tung- 

 chiao-cheng, King-shan-hsien. There is still another specimen (PI. VIII., Fig. 5.) of 

 the same species was colleced from Heh-chia-tzui-tze {^M^%.=^) 6 h north-west of 

 Chang-chia-chi, Chung-hsiang-hsien, (Coll. W. P. Shu and C. C. Yii). 



r. J. Barrande: Syst. Sil. de la Boheme, vol. II., Texte III, p. 432, pi. 373, pi. 399. 



