October, 1913. New Trilobites — Slocom 57 



T. ovata Clarke, 1897. Pal. Minn., Vol. Ill, pt. 2, p. 716, figs. 17-19. 



Body broadly ovate, widest at the base of the cephalon, distinctly 

 trilobed, length about equal to the width at the eye lobes. 



Cephalon broadly semicircular on the anterior margin, very, highly 

 convex. Dorsal furrows clearly defined on the posterior third of the 

 cephalon, obsolete in front. Glabella convex between the dorsal fur- 

 rows, not defined in front. Eyes small, pedunculate, extending laterally 

 and horizontally. Occipital segment and furrow very faintly marked, 

 rounded backward. Free cheeks small, produced laterally at the genal 

 angles into blunt spines. The facial sutures rise rapidly from the posterior 

 margin to the summit of the eye lobes, thence round gradually forward 

 to the anterior margin, which they intersect in front of the dorsal furrows. 



Thorax wider than long, tapering, composed of ten smooth, slightly 

 convex segments. Axial lobe depressed convex, narrower than the 

 lateral lobes, 'segments arched forward. Pleurae flat for more than half 

 their width from the axis, then bent downward, segments strongly 

 recurved toward their extremities. 



Pygidium nearly flat on top and curving abruptly to the margins, 

 short, subquadratic. The posterior margin forms a very broad curve, 

 width about twice the length. Axis prominent, narrower than the 

 thoracic axis, tapering slightly and terminating bluntly in an elevated 

 extremity, which is faintly bilobed; axis entirely surrounded by the 

 dorsal furrows; annulations of the axis nearly obsolete. 



The surface of the cephalon is covered with epidermal punctae 

 except in the dorsal furrows and on the palpebral lobes. On the cheeks 

 and anterior portion of the glabella the punctae are vertical and isolated, 

 on the posterior surface of the glabella they are oblique and crowded. 

 The surface of the thorax appears to be smooth. Doublure marked 

 with prominent lines parallel to the anterior margin. Pygidium sparsely 

 punctate on the posterior margin but on the anterior portion the 

 punctations are deep, coarse, and arranged in transverse rows. 



The foregoing description is based on a practically complete speci- 

 men from the Platteville beds at Mineral Point, Wisconsin, in the 

 paleontological collection of the University of Chicago. The Fayette 

 County specimens have been compared with the Platteville specimen 

 and agree so well that they must be considered to be specifically identi- 

 cal, although previously /. ovata has been found only at lower geological 

 horizons. 



This species is represented in the Museum collections from Fayette 

 County by a nearly complete cranidium from the Lower Maquoketa at 

 Clermont and another from the Upper Maquoketa at Patterson's 

 Springs. 



