24 



Trilobita. 



Gn. et SP. INDEX. 



PI. XVI., Fig. II. 



Thorax with 7 or more transverse segments ; a.xial lobe moderatel)' con- 

 vex, sh'ghtly broader than half the breadth of the pleural lobe, and gradually 

 narrowing posteriorly. Pleurae nearly flat, horizontal and at right angles to 

 the a.xial lobe, out to the geniculation, where the)- bend downward and back- 

 ward, terminating in a falcate extremit)- ; pleural furrow long and broad, 

 starting at the dorsal furrow near the front and e.Ktending out on the falcate 

 end. The free pleural extremity of the last segment is considerabl}' larger 

 than those anterior to it. 



The cephalon and the greater part of the pygidium are missing ; the 

 small part of the latter found attached to the thorax indicates that the pygi- 

 dium, when complete, attained a considerable size. On the specimen, it shows 

 two rings, with the cylindrical axial lobe and a flattened lateral lobe preserv^ed ; 

 with two curved interpleural furrows ; each rib of the lateral lobe is distinctly 

 marked by a narrow^ pleural groove ; the character of the margin is unknown. 



Dimensions : — The fragmental specimen, figured, is some 30 mm. long; 

 the axial lobe of the thorax, after restoration, measures 10 mm. in maximum 

 breadth, and the pleural lobe 16 mm. 



The preservation of the pygidium is so incomplete that the segments 

 considered above as belonging to the pygidium may with equal right be as- 

 signed to the thorax ; if this be not the case, the resemblance of the present 

 specimen to Ptychoparia is considerable. No other fossils being found in as- 

 sociation with it, and the stratigraphical order of the rock from which it was 

 collected being unknown, I have at present no other means of determining 

 the geological age of the present fossil, though it certainl}- belongs to the 

 Older Paleozoic and most likely to the Cambrian. 



' Locality : — Lan-hsi, Chen-chou-fu, prov. Hu-nan ; in a dark gfey com- 

 pact calcareous argillite. 



