314 THE SILURIAN TRILOBITES OF NEW SOUTH WALES, 



in front of the glabella, striated at the side of the free cheeks ; 

 glabella conoid, obtusely pointed forwards, very moderately convex, 

 no lateral furrows visible ; neck furrow narrow, straight ; neck 

 segment rather wide, gently arched, sub-tumid at each extremity ; 

 axial furrows rather faint ; facial sutures from the eyes to the 

 frontal margin straight, thence outwards at an angle of about 60°, 

 curved posteriorly, and cutting the posterior margin about the 

 middle of the side lobes of the cephalic shield; fixed cheeks small, 

 with large eye-lobes ; eyes large and crescentic ; free cheeks 

 moderately large, with a well denned and striated margin ; genal 

 angles continued into stout spines, which reach to and include the 

 fourth pleura of the thorax. Thorax of nine segments, with 

 rather straight lateral margins, length equal to the combined 

 width of the pleurae ; axis at its anterior end much wider than 

 the side lobes, posteriorly they are equal, moderately arched : 

 segments inclined slightly forwards ; axial grooves distinct and 

 narrow; pleurae moderately arched, distinctly grooved, the grooves 

 widest medially, diminishing towards the proximal and distal 

 ends. Pygidium large, subelliptical or triangular, proportion of 

 width to length as about 16 : 14; axis prominent, terminated 

 distally somewhat abruptly and obliquely, twice as wide at the 

 proximal as the distal end ; segmentation faint, of eight or nine 

 rings ; axial furrows moderately distinct ; pleura? five, wider than 

 the axis, less arched than those of the thorax, and the first three 

 pairs distinctly furrowed; limb wide, striate, and slightly thickened. 

 Obs. — Additional specimens enable us to form a much better 

 idea of the structure of this Trilobite than when it was 

 originally described. The principal characters of the species are 

 a conoid glabella, ill-defined glabella furrows, moderately large 

 genal spines, a thoracic axis of nine segments, the axis of the 

 pygidium of eight or nine, and the pleurae of the same five in 

 number. The original specimen of P. boioninyensis figured was 

 one in which the mutilated cephalic shield was in the form of an 

 impression, and the pygidium as a decorticated relief. The test 

 of this shield is beautifully ornamented with anastomosing lines, 

 which on the genal angles and base of the spines become concentric 



