(]) 42 Pohconlnlogla Shiico '^'"i'- B 



The siphuncle is filled solidly with the ondosiphosheaths Imt those have been 



converted into crystalline lime. The upper portion of the specimen however shows 



the endosiphocone or funnel-like prolongation of the living-cliamber into the siphuncle, 



bounded by the last endosiphosheath. This part of the specimen is partly tilled with the 



lime matrix in which the shell is embedded. Endosiphuncle unknown. 



The sides of the siphuncle are distinctly marked by the necks of the septa, and 

 those show that the later ones extend beyond the upper edge of the preceding one, thus 

 showing that the shell belongs to the genus Vaginoceras. The direction of the septal lines 

 is strongly oblique, forming an angle of about 50'' with the axis of the siphuncle and 

 meeting on the ventral side in an angle of about 70°. This indicates that the siphuncle 

 is subventran in position. The septa average al.)0ut 3.3 mm. apart. 



The sulicylindrical character of this siphuncle is its most marked feature, and this 

 togothor Avith the obliquity of the se])tal lines, and their relative closeness, serve to 

 differentiate this species from others found in the Ordovician beds of China.* In the 

 characters noted_, our species is not unlike the early stages of Varjinoceras oppleturn 

 Ruedemann, from the Chazy beds of the Lake Champlain region of the eastern United 

 States, but there is no indication that the Chinese species ever reached the size of the 

 adult American form. 



HoRizOiSr AXD Locality: In the upper quarry liods of the Machiakou limestone, 

 associated with Aetirioccms, Lopho^^pira etc.. Cement quarry Tangshan. Survey 

 expedition coll. 



Family PILOCERATIDyE Hyatt 



Genus PiLOCERAS Salter 



Piloceras platyventrum Grabau (sp. nov.) 



Plats IV, Figs. 11 a-o, 12x-c. Text figures 1 a-e. 



Siphuncle with broadly subconical apex with endosii:)huncular scar or shghtly 

 protruding endosiphuncle; enlarging rapidly until at "a point 15 mm. from the apex (in 

 (ino specimen fig 11), it has reached a diameter of 24 mm., after which it enlarges more 

 gradually at tlic rate of about 15 mm. in 10 of length, while later on it appears to be 

 sulicylindrical. The apical portion of the siphuncle (for about ;!5 nim. in the onlv 

 specimen showing this part) appears smooth, this part ending in a faint broad but 



* Several species occur in the Ordovician rocks of sontli China. These will be described in a fuhirc niimbcj' of 

 this publication. 



