708 SILURIAN TRILOBITES, 



modertately tumid and arched, sloping very gradually into the 

 front marginal and neck furrows, frontal expansions triangular, 

 very moderately tumid, and their apices reaching the anterior 

 j)oints of exit of the facial sutures; first pair of lateral lobes 

 absent, median pair subconical or subtriangular, of moderate size, 

 very moderately tumid, basal pair large, subquadrate, with 

 rounded outer margins; first pair of glabella furrows deep and 

 wide, second pair shallow towards the axial furrows and deep 

 towards the false furrows, both pairs uniting the axial furrows with 

 the false furrows; false furrows wide and deej); axial furrows very 

 wide, distinct, shallow along the median portions. Fixed cheeks 

 large; genal lobes large, ridged, tumid, subtriangular, united to the 

 lateral lobes of the neck ring by the genal ridge, and falling 

 abruptly into the lateral extensions of the neck furrow, bearing 

 some very large tubercles. Genal or palpebral furrows moderately 

 distinct and highly tubercled. E3^e or palpebral lobes large, very 

 prominent and triangular. Ocular ridge very prominent and 

 overhanging the facial sutures. 'Ejefi small proportionate]}^ 

 subpedunculate, fixed obliquely outwards and very slightly 

 forward, i^emarkably near the front margin, ^ery wide apart, the 

 distance between therr being equal to the diagonal from the base 

 of a genal spine, and the point at which the facial suture cuts the 

 front margin on the opposite side of the glabella, or one and a 

 quarter times the length of the cephalon. Neck furrow wide and 

 shallow behind the central glabella lobe, narrow and deep between 

 the basal glabella lobes and the lateral lobes of the neck ring; its 

 lateral extensions (as are the axial furrows also) are interrupted 

 by the genal lobe ridges, and from the genal lobe ridges they extend 

 widely and deeply to the bases of the genal spines, thence bend 

 anteriorly, passing (deeply under the eyes) to the front marginal 

 furrows. Neck ring veiy wide and very moderately arched verti- 

 cally, but greatly so posteriorly. Occipital spines strong, long, 

 and originating in the median transverse line of the neck ring, 

 extending upward and outward for the first part at an angle of 

 60°, then arching backward and inward and the ends sharply 

 deflected. Facial sutures soldered, but indicated anteriorly along 



