148 Carl O. Dunbar, 



rounded shoulder, and broadly concave forward across the base 

 of the whorl. 



Ditneusioiis: Height, 37 nini. ; width, t,t, mm. ; height of aper- 

 tin-e, 27 mm. ; width of same, 20 mm. 



Occurrence: Rockhouse shale, at Rockhouse, on Horse Creek, 

 Hardtn County. 



CLASS CRUSTACEA 



Subclass Trilobita 



family phacopid^ 



Dalmanites purduei, n. sp. 



Plate V, figs. I, 2 



Description: Species of very large size. Cephalon semi- 

 elliptical, with moderately long sharp genal spines and with a 

 slight prolongation of the anterior margin in front of the gla- 

 bella. Glabella large, depressed convex, most elevated between 

 the palpebral lobes, and descending with even curvature to the 

 front. Front lobe transversely elliptical, a trifie over three-fifths 

 as long as wide, and marked by three shallow subcircular pits. 

 The deeper of these is in the median line and just back of the 

 center of the lobe, while the others are so shallow as to be 

 scarcely visible, and one is near the center of each lateral half of 

 the lobe. 'J he first glabellar furrow deep and extending nearly 

 three quarters of the distance to the axis. The second, third, 

 and fourth glabellar lobes are well fused at their extremities, the 

 second and third lateral furrows being reduced to mere oblong" 

 pits tipon the glabella. Cheeks with rather strongly arched 

 slopes and with a gentle concave zone' bordering the margin. 

 Occipital furrows deep and wide. Eyes large and elevated. 

 Lateral facial sutures lying in a distinct groove. Siu'face in all 

 the specimens exfoliated, but the cast of the free cheeks rough- 

 ened by shallow dimples. 



Pygidium subtriangular in outline, and ending in a blunt 

 spine. Number of segments in the axial lobe varying from 

 seventeen in a small specimen to twenty-two in the largest one. 



Dimensions: A mature cephalon measures 81 mm. from occi- 

 pital ring to front margin; 130 mm. across the head at the eye 

 lobes, 60 mm. between the eyes. The largest pygidium has a 



