496 SILURIAN TRILOBITES, 



and small; intercalary ring nodular; axial grooves deep and wide; 

 neck furrow distinct, and continued across the lateral lobes very 

 distinctly; neck ring robust and bearing centrally a spine of 

 varying size, corresponding with the thoracic axial spines, bases 

 nodular ; lateral lobes small, triangular, tumid, borders thickened, 

 their measurement from genal angles to the front of the axial 

 grooves equal to half the front width of the glabella; posterior 

 facets strongly ridged; palpebral lobes conspicuous, highly arched, 

 outwardly bounded by distinct narrow borders, granulate; palpe- 

 bral grooves very distinct, deep at front and back and thus 

 contracting the genal lobes, passing posteriorly round and under 

 the eyes into the lateral extensions of the neck furrow, adding 

 relief to that organ; genal lobes tumid and deltiform; genal angles 

 rounded and faceted; when the thickened borders fall out deep 

 grooves are left. Eyes equal to half the length of cheeks, seventeen 

 rows of lenses, the maximum number in a row being five; cornea 

 and walls of cups thick; lentiferous face, anterio-posteriorly, has a 

 semicardiod curve. 



Thorax. — As wide as long, very gently contracting posteriorly, 

 sides almost perpendicular, smooth; axis sharply ridged, rings 

 nodular at bases and centrally bearing strong, short recurved 

 sjDines; when decorticated it is semicylindrical, as wide as 

 side lobes (not measuring the contour of lobes); axial furrows 

 moderately distinct; side lobes horizontal between axial grooves 

 and fulcra, pleuraB slightly recurved, ends rounded in at the 

 posterior angles; medial grooves distinct, reaching beyond the 

 middle of the deflected ends in decorticated specimens, and 

 triangular posterior ridges strong; little or no trace of granulation 

 on any portion of the thorax. 



Pygidium. — About semicircular, highly inflated; axis very 

 prominent anteriorly, and terminating indistinctly at the inner 

 edge of the border at about half of its anterior width, slightly 

 depressed between the side lobes, shows eight rings and a 

 terminal piece; the first three rings bear nodules centrally corres- 

 ponding to the spines of the thoracic axis and are arched forward; 

 each succeeding one becomes less distinct until the last is very 



