Vol. I. C. C. Yu — Ordovician Cephalopoda of Central China (ii) 37 



The interior of the camerfe are deprived of any deposit except the margins of the 

 ectosepta, on which the stereoplasm is slightly and irregularly deposited. Ectosepta 

 very thin, having a concavity a Httle less than one camera. 



The endoconch is in contact with the outer shell. It is cylindrical in longitudinal 

 section and circular in* transverse. It appears to remain about lo mm. in diameter 

 throughout the whole length of the fragment preserved, so that it occupies nearly 1/2 

 the diameter of the ectoconch at the lower fragmentary end and 2/5 at the upper. No 

 endosepta are seen. The endotheca is absent and the inner shell is confined by the 

 continuation of the imbricating tubi, which in this specimen seem not so long as 

 those in the form figured by Holm. 



RicMARKs. This species is characterized by its remote and almost equal 

 ectoseptal distances, and cylindrical and large endoconch. Even though we know 

 nothing about the apical end of our shell, no form comes nearest to the present specimen 

 other than V aginoceras belemniforme Holm from the upper red Orthoceras Limestone on 

 the island of Oeland. 



Horizon and Locality: From the red limestone bed of middle Ordovician 

 age in the upper part of the Tafang limestone near Ta-fang village, Yang-sing-hsien. 

 The specimen was collected by Mr. C. Y. Hsieh. 



Vaginoceras shui Yu (sp. nov.) 

 Plate IV., Figs. 3a-b. 



Ectoconch of unknown size, slender, subcylindrico-conical. Cross section 

 circular. Endoconch moderately large, submarginal. Both the apical end and the 

 basal extremity unknown. 



Ectosepta remarkably gently concave, about one third as deep as the camene. 

 The ectoseptal distances slightly increase from 6 mm. at the lower preserved end to 8 mm. 

 at the upper, while the corresponding width of the ectoconch are 14 mm. and 19 mm. 

 respectively (The real diameter of the ectoconch would be greater than this, because the 

 section is not in the median plane). 



The endoconch is circular? and situated near the margin of the ectoconch. Its 

 diameter is little less than one third that of the outer shell. It is completely surround- 

 ed by camer«3 and distinctly marked by the tubi By the aid of a lens we can see the 

 tubi are so long that they overlap backward beyond the preceding ectoseptum extending 

 even to the third one. Inside the endoconch a concial funnel-shaped endoseptum is 

 included with the deposit of crystalline lime below. 



