(i) oS Palxonlologia Sinica Scr. B 



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

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

 shell not being visil.ile. 



Tliree fragments of the collection appear to represent parts of a single siphuncle 

 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 y<) mm. At the smallest 

 end preserved, the diameter is 6.") mm., at the largest 9 mm. The rate of tapering is 

 about 1 mm. in 'I'k The youngest fragment is slightly flattened ventrally and shows 

 broad ill-defined undulations. It has a sub-central endosiphuncle, and tlie organic lime- 

 filling (stereoplasm) of the remainder is ob:-eurel3' radiate. In the larger fragments, the 

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

 ness. In^certain positions, however, very faint oblique hues are visilde, suggesting septation. 

 Within it, is at least one well-defined thick-walled conical slieath, 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 witlr 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 1.*') mm. and a liasal 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 carl>onate is als(j rahate. The presence of three 

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

 radiate) lime-filling, l)ut these were exceedingly thiji walled, pussibly membranous. * 



Except for tlie very faintly indicated oblique ridges these siphuncular fragments 

 suggest the preseptate apical end of I*r(jlt'rorarncro(xra^, and for such they wer(.' 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 camera- 

 (Plate IV fig 2). 



HoRizux AXD Locality : This species occurs in the Lower Ordovician Peilintze 

 limesl(jne of Pei-lin-tze, Shih-Mun-Ohai region near Ghingwangtao eastern Chihli. It is 

 associated with Cldhliucerax, Airlnvocijatlms etc. Collected by F. F. Mathieu, in whose 

 honor the sjjecific name is given. 



* Tliis supports Rucdemann's contrnii^n that endosb^aths aro prcs.Mit ia (_'<uiiri\iri:rits (including Proli'mcaniL-nr 

 cerax), below the final thicli-walled sheath of the adult living-chamber. At least one of tlicfc iu 1he prcscnl spccimin, is thict;- 

 walled and of well defined character. 



