314 NORTH AMERICAN INDEX FOSSILS. 



Margin of cephalon and thorax spinose. Pygidium small, with 

 very wide axis. (Type of genus.) 

 Chazy of Vermont, New York, etc. 



Order PROPARIA Beecher. 

 LX. Encrinurus Emmrich. 



Cephalon tuberculated. Glabella prominent, slightly spindle- 

 shaped, its furrows indistinct or absent. Free cheeks narrow, 

 separated anterior to the glabella by a small plate. Eyes small, 

 placed on short, conical prominences. Thorax of ii segments. 

 Pygidium elongate, triangular, numerously segmented. Ordovicic 

 and Siluric. 



151. E. trentonensis Walcott. Ordovicic. 

 Pygidium differs from that of E. ornatus in lacking the depres- 

 sion along the median line of the axis, and each third or fourth of 

 the 25 annulations bears a median tubercle. The nine or ten ribs 

 on the side lobes curve backward very strongly and are not marked 

 by tubercles. Axis of pygidium terminates within the posterior 

 margin. 



Trenton of New Jersey, Illinois, Wisconsin, etc. 



152. E. ornatus Hall and Whitfield. (Fig. 1627.) Siluric. 

 Cephalon strongly pustulose. Glabella pear-shaped. Pygidium 



with depression along middle of axis, marked with tubercles at 

 intervals ; also the pleural segments tuberculate. 



Niagaran of Maine, New York, Ohio, Indiana, Arkansas, Ten- 

 nessee, Alabama, Quebec, etc. 



LXI. Calymene Brongniart. 



Cephalon with a thickened margin. Glabella conical, broadest 

 behind, very convex, divided by three pairs of deep lateral fur- 

 rows, forming three globular lobes on each side. Eyes small. 

 Facial sutures curving strongly outward, and cutting the lateral 

 margin (see Fig. 1624, b, d). Thorax of 13 segments; axial 

 furrows deep. Pygidium of six to eleven segments, usually 

 not distinctly marked off from the thorax. This genus possessed 

 very prominently the power of enrollment. Ordovicic-Devonic. 



