Vol. I. C. C. Yu — Ordovician Cephalopoda of Central China (ii) 47 



Siphuncle central, narrow, measuring about i/io the diameter of the shell. It is 

 circular in transverse section. It is entirely empty in some specimens, but partly filled 

 with the secondary crystalline deposit in others. The margins of the septa are either 

 perfectly free from any deposit or lined with a layer of stereoplasm, which is sometimes 

 very thick and sometimes rather thin as well as irregular. The cameme are filled with 

 crystalline calcite of secondary origin, but generally empty. 



A very small part of the test has been preserved, showing the transverse lines 

 of growth. 



There is another specimen (Plate V., Fig. 7), which was collected 

 from the same locality and probably belongs to the same species. It is represented 

 by a fragment of the apertural portion, having a length of 70 mm. The living 

 chamber is partly preserved with three adjacent camene. The septal distance 

 measures'15 mm. at the lowest camera of the fragment, and 10 mm. at the uppermost 

 or last one, where the corresponding measurements of the diameter of the shell are 32 

 mm. and 36 mm. respectively. The surface is ornamentated by well marked transverse, 

 flexuous, imbricating strife, of which three are counted in a distance of 2 mm. The 

 other internal characters of this individual are the same as those of the preceding one. 



A third specimen (PL VI., Fig. i.) is robust in form. It measure about 210 mm. 

 in length. The living chamber is partly preserved and the apical portion is missing. 

 The septal distances continually and gradually increase from the lower part of the 

 shell toward the aperture, "being little more than 1/2 the diameter. Up to the third 

 camera from the Hving chamber, it stops to increase and gradually reduces upwards, 

 where the depth of the cameree is less than 1/2 the diameter. The septal necks are 

 slightly shorter than 1/2 the septal intervals. Test not observed. 



The body chamber in a fourth specemers (PI. VI., Fig 2) is rather large. 

 Because of the incomplete state of preservation its full length can not be made out, but 

 the portion remaining reaches a length of 48 mm. or more than t| times the diameter 

 of its base. The septal distances of the mature portion seem to be greater than those 

 in the preceding specimens, measuring about 4/5 the shell diameter. The septa also 

 become crowded as they approach the outer chamber. The test is not preserved, but 

 the surface character may be seen on the mold of the interior, which is marked by 

 regular, flexuous transverse lines of growth. The actual surface had its strite arranged 

 similarly, but they appear to have been much closer together. There is another small 

 specimen (PI. Ill, Fig.5.) which indicates the young stage of the same species. 



Remarks. In the collection about ten specimens of this species are found, but 

 there is a great variation in tapering between them. Some taper at the same rate as 

 that of Foord's specimen, and others much more rapidly, varying from 1:6 to 1:8. 



