Vol. I. C. C. Yu — Ordoviciari Cephalopoda of Central China (ii) 25 



Under is very large and its major diameter is practically equivalent to 1/2 that of the 

 ectoconch. In a favourable light the endotheca may be clearly seen along the inner side 

 of the invaginated tubi. 



Comparison: So far as we know, the form, which bears the closest resemblance 

 to this specimen, is Cameroceras tenuiseptum Hall. The transverse sections of the 

 ectoconch and the endoconch of Hall's species are circular, but those of the present form 

 are both elliptical. Moreover, the ectosepta of the latter are comparatively more widely 

 separated than are those of the former. 



Horizon and Locality: This variety was obtained by J. L. Smith and C. Y. 

 Hsieh respectively from the upper part of Neichiashan formation at Nei-chia-shan 

 near Sin-tan, Tze-kuei-hsien. 



Cameroceras hsiehi Yu (sp. nov.) 

 Plate I., Figs. 4a-b. 



Shell straight, slender, gradually tapering at the rate of i in 10. The cross section 

 of the ectoconch is elliptical, having its two diameters at the ratio of 11:9. Neither 

 extremity preserved. The septate fragment measures little less than 80 mm. in length. 



The interspaces between the ectosepta are rather short, being about from 1/6 to 

 1/5 the longer diameter of the ectoconch. They are 3.5 mm. distant from each other in 

 the lower preserved end and 6 mm. in the upper, while the corresponding longer diame- 

 ters of the ectoconch are 22 mm. and 30 mm. respectively. The ectosepta are very deep, 

 with a concavity equal to the depth of one and one half camerte. The tubi have a 

 length of more than one camera. 



The endoconch is large, about one third the longer diameter. Under the magnifier 

 we can clearly see that along the inner sides of the tubi the endotheca characteristic of 

 the genus Cameroceras is present. The endoconch is perfectly circular in outline. Its 

 position is in contact with the ectoconch. Only the last endoseptum is exposed, and the 

 space below it is wholly filled with calcite. The sides of the endocone seem to be 

 undulating. 



In the empty camene there is a slight and irregular organic Ume-fiUing deposited 

 along the margins of some ectosepta. Test not preserved. 



