FOSSILS OF THE LOWER SILURIAN. 241 



surrounded on the margins by twelve short, rather strong sjiines, the four 

 on the posterior margin being shoiter than the others. Axis narrow, highly 

 convex, two-thirds as long as the shield, and marked by four rings, exclu- 

 sive of the terminal ones. Lateral lobes broad, convex, and marked by four 

 low, rounded ribs, the anterior one much narrower than the others; each of 

 the four ribs terminating in one of the lateral spines. 



There can be no doubt that the above-described pygidium belongs 

 to the same species with the associated glabella, as they are both equally 

 abundant, and are the only trilobitic remains brought from the locality, 

 except those of ConocephalUes subcoronutus. The glabella is enlarged to 

 three diameters in the figure, while the i)Agidiuni is given natural size, l)ut 

 is one of the largest individuals seen; while there are fragments of glabellas 

 in the rock fully twice the size of the specimen figured. The S])ecies bears 

 a very close resemblance to D. gotlticus, herein described, but ditfers princi- 

 pally in the simple ribs; while in that species they are divided, a feature 

 that will very readily distinguish the two forms. 



Formation and locality. — In limestone of the age of the Quebec group, 

 from the base of Ute Peak, Wahsatch Range, Utah. Collected by Arnold 

 Hague, esq. 



DlKELLOCEPHALrS WAHSATCHENSIS 11. sp. 



Glabella elongate-quadrangular, with parallel lateral margins and 

 slightly-rounded front ; height and width about as four to three ; very 

 depressed-convex, and marked by two i)airs of transverse furrows, which 

 do not quite meet in the center, dividing the glabella into three nearly 

 equal portions. Occipital furrow narrow, not strongly defined ; ring nar- 

 row, distinct, and bearing a slender spine on the center; dorsal farrows 

 narrow and i)oor]y defined. 



Fixed cheeks wide and flattened ; ocular ridges faintly marked, rising- 

 opposite the anterior furrow of the glabella, and directed slightly backward 

 to the eye-lobe. Fi-ontal limb very short and wide, the marginal rim regu- 

 larly arcuate, narrow, and prominent, closely cutting the front of the 

 glabella. Facial sutures not fully determined, but are distinct on the 

 anterior margin, cutting the rim with a strong outward curvature, and again 

 10 p n 



