(0 38 Palxontologia Sinica Ser. B 



On the exterior of the shell there appear to be broad very shallow and ill-defined 

 concentric constrictions, but these are observed only on the ventral side, the rest of the 

 shell not being visible. 



Three fragments of the collection appear to represent parts of a single siphunclc 

 of this species (Plate IV fig 3a-c). This is long and slender, but its entire length is not 

 known, though the fragments preserved indicate a length of over 80 mm. At the smallc.-t 

 end preserved, the diameter is 6.5 mm., at the largest 9 mm. The rate of tapering is 

 about 1 mm. in 25. The youngest fragment is slightly flattened ventrally and shows 

 broad ill-defined undulations. It has a sub-central endosiph uncle, and the organic lime- 

 filling (stereoplasm) of the remainder is obscurely radiate. In the larger fragments, the 

 shell is circular in section, and appears entirely smooth, and is half a millimeter in thick- 

 ness, lacertain positions, however, very faint oblique lines are visible, suggesting septation. 

 Within it, is at least one well-defined thick- walled conical sheath, tapering at the rate of 

 1 mm. in 10. Around this the crystalline lime has a radiating structure. The interior of the 

 cone, formed by the sheath, is also filled with crystalline calcite, except at the larger end 

 (3b), where an open semilunar cavity exists, due to removal of softer filling. At the upper 

 end of the largest fragment this has a vertical diameter of l.G mm. and a basal width of 

 4.8 mm. On the other side of the fragment, which is 20 mm. long, this semilunar tube, 

 here still retaining its filling, has been reduced to about half these dimensions. The 

 structure of the interior filling of calcium carbonate is also radiate. The presence of three 

 other sheaths is indicated by concentric tubular interruptions of the crystalline (generally 

 radiate) lime-filling, but these were exceedingly thin walled, possibly membranous. * 



Except for the very faintly indicated oblique ridges these siphuncular fragments 

 suggest the preseptate apical end of Proterocameroceras, and for such they were at first 

 taken. This is also suggested by the circular cross-section, but on the other hand, their 

 size agrees with that of the siphuncle of the species where still surrounded by the camene 

 (Plate IV fig 2). 



HORIZON AND LOCALITY: This species occurs in the Lower Ordovician Peilintze 

 limestone of Pei-lin-tze, Shih-Mun-Chai region near Chingwangtao eastern Chihli. It is 

 associated with Chihlioceras, Arclncocijathus etc. Collected by F. F. Mathieu, in whose 

 honor the specific name is given. 



* This supports Ruedemann's contrnlijn that endoshoaths aro present in Camerocerai (including Prvterocamero- 

 cerai}, below the final thick-walled sheath of the adult living-chamber. At least OEC of these in 1he present specimin, is thick- 

 walled and of well defined character. 



