BY R. ETIIEHIDGE, JUNR., AND JOHN MITCHELL. 499 



and sloping upwardl^y at an angle of 60° to 70°; height of each eye 

 about two-thirds of its length, in front barel}'' reaching the front 

 angles of the glabella, posteriorly in a line with the central por- 

 tion of the intercalary furrow. 



Thorax. — Of eleven segments, width seems a little greater 

 than length; axis j^rominent, contracts very gradually posteriorly 

 from the sixth segment, terminating with a width about 

 four-fifths of the anterior width; segments nodular at the 

 ends; lateral lobes very little wider than the axis, hori- 

 zontal between fulcra and axial furrows, deflected portion 

 steep, component pleurse imbricate and rounded at the ends; 

 pleural furrows distinct and wide, seeming to reach nearly to 

 the ends; anterior ridges of pleurpe triangular, posterior very 

 narrow; interpleural sutures and axial furrows distinct. 



Pygidium. — Subsemicircular or subquadrilateral, width greater 

 than twice the length; axis tolerably prominent, seven seg- 

 ments visible, terminating bluntly with about half the anterior 

 width at the border, slightly sunk between the lateral lobes, 

 which are moderately inflated, horizontal between fulcra and 

 axial grooves, anteriorly deflected to corresjDond with pleurae of 

 thorax, but posteriorly becoming less steep; five to six pleurae 

 visible on each lobe, only the two anterior ones showing the pleural 

 furrows and sutures distinctly, the furrows reach the border, 

 anterior face straight, axial grooves moderately distinct. The 

 whole surface shows evidence of granulation. 



Ohs. — This species approaches P.feciLndus, Barr., very closely, 

 but we consider there are suflicient differences between them to 

 justify us in giving specific rank to our form. Its most con- 

 spicuous feature is the great size of the e3'es, in which resi3ect it 

 surpasses P.fecundus, Barr., and many other species of the genus, 

 and as in all the mature specimens that have come under our 

 notice, twenty-two vertical rows of lenses containing twelve in 

 each row are constant features, while in P. /ecundns, Barr., 

 nineteen vertical rows with nine lenses in a row^ are the normal 

 features, we consider this to be a sufficient difference for specific 



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