(ii) S2 Palxontologia Sinica Set. B. 



that the long tubi extend beyond the space of one camera. According to the statement 

 of Hyatt the generic name of Foord's species should be changed into F«gmoce?'as. As 

 to the specific identification, the characteristics of our specimen strongly resemble 

 Foord's species, but the ectosepta become more crowded in the adult stage, which is not 

 the case in Foord's form. Nevertheless, this feature may be considered as a minor 

 point due to senility, and can not serve to characterize a distinct species. 



Horizon and Locality: Collected from the upper part of Neichiashan forrftation 

 at the northern side of Tai-hung-shan {-k H ill) about one mile or more to the west of 

 the city of Nan-chang-hsien. According to Foord's description Vaginoceras wahlenbergi 

 belongs to Arenig in Sweden, Norway, Russia and other locahties in Europe, but this is 

 incorrect, the horizon being late Middle Ordovician'. (W. P. Shu and C. C. Yii Coll.) 



Vaginoceras wahlenbergi Foord var. cylindrica Yii (var. nov.) 

 Plate IV., Figs, i, 2a-b. 



Ectoconch robust, cyUndrical. Endoconch large, situated nearly close to the 

 margin of the outer shell. This variety is represented so far only by a fragment 

 belonging to the upper part. The cross section of the endoconch is circular, but that of 

 the ectoconch is quite obscure, though it is probably circular too. Rate of increase 

 about I in 12. 6. 



Ectosepta moderately concave with their depth scarcely exceeding two thirds of 

 the camera. The ectoseptal intervals become gradually and slightly longer in distance 

 apart as the ectoconch advances in age, measuring 15 mm. apart near the lower end 

 and 17 mm. near the upper, or about two fifth the diameter of the outer shell. 



The endoconch is prolonged into a nearly cylindrical endocylinder. Its diame- 

 ter is a little less than one third as wide as that of the ectoconch. In the actual 

 measurement the diameter of the ectoconch attains 40 mm. at the lower end, whereas 

 the corresponding diameter of the endoconch is 12.5. The invaginated tubi are dis- 

 tinctly visible. No endoseptum has been found, the endoconch proper not being 

 preserved. Stereoplasmic deposit often occurs on the margins of the ectosepta, this 

 being about i mm. thick. 



I. See stratigraphic part, pp. 20, 21. 



