Vol. I. 



C. C. 



Yu—Oydovician Cephalopoda of Central China 



;ii) 41 



'^^■' 



Fiii 



F'g- I- Fig, 2. 



Fig. I. Vaginoceras reedi. F.xtcrnal view ot a fragment of tfic ectoconch witfi a part of the 



endoconcti exposed. Natural size. 

 Fig. 2. Vaoinoceras reedi. Longitudinal section of the same, sfiowing the large, empty 



endoconch and the closely set ectosepta. Natural size. ■ .; ; 



Fig. 3. Vaginoceras reedi. End view of the same. Natural size. 



Associated with Vaginoceras neichianense, there are many specimens which are 

 represented either by the fragmental phragmacone or the endoconch only. But some of 

 them are known from a part of the septate portion with a large endoconch projecting 

 out of the middle part. The ectoconch is straight, cylindrical and slightly elliptical in 

 cross section. Owing to the fact that the fragment of the ectoconch is very short and 

 not well preserved, the rate of increase can not be determined, nevertheless it appears to 

 be very gentle. 



The ectosepta are very closely arranged. The ectoseptal interspace measures 3 

 or 4 mm. apart, where the ectoconch has a longer diameter of nearly 30 mm. The 

 ectoseptal sutures are slightly undulating. Camene entirely free from any deposit, 

 and ectosepta strongly concave. 



The endoconch is very large, having a diameter of V2 that of the ectoconch or 

 more. It is slightly distant from the center. Its cross section is circular. The lono- 

 tubi are prolonged backwards beyond the next preceding ectoseptum. Neither the 

 deposits nor the endosepta are found inside. 



In another fragmental specimen (PI. I., Fig. 11) of 30 mm. in length the endoconch 

 is larger, measuring 19 mm. in diameter, where the ectoconch has a longer diameter of 35 

 mm. At the same stage the ectosepta are 3 mm. apart. 



Orthoceras sp.' described by Yabe and Hayasaka is apparently of the same 

 species. They stated "The specimen is a fragment of a cylindrical shell, in state of 

 internal cast, and 50 mm long; it is oblong in cross section, measuring 29 mm, and 24 mm. 

 in larger and smaller diameter respectively. The surface of the stone nucleus is smooth. 



I. 



]oc. cit. 



