REPORT OF THE STATE PALEONTOLOGIST I903 295 



TRILOBITA 

 Genus cheirurus Beyrich \ 



Cheirurus mars sp. no v. 



Plate 5, figures 1-2 



Description. Glabella somewhat resembles a medieval, conical 

 helmet, rising from the frontal rim with a curve of about 6mm 

 radius for one third the distance to the apex of the cone. In the 

 other two thirds the convexity becomes markedly less and the apex 

 is approached with but very slightly convex outlines ; from the apex 

 to neck furrow the outline is at first concave and then straight. 

 The cone or spur is thus rather high and produced backward over 

 the neck ring. Length from frontal, furrow to neck furrow 13mm, 

 from frontal furrow to apex of cone 15mm, hight of apex of cone 

 above neck furrow about 8mm, width of glabella just in front of 

 the neck ring nearly 12mm. The glabellar furrows are convex 

 toward the front throughout their length; the two anterior pairs 

 reach to a little less than one fourth the distance across the glabella ; 

 the middle one is most convex toward the front; the posterior fur- 

 row is less bent at first, reaches about halfway to the apex of the 

 cone and is bent so as to meet its axis at an angle of about 70°. 

 Marginal furrow of glabella rounded in front, distinctly angled as 

 it turns to pass along the sides, where it is concave toward the under 

 surface with a radius of about lomm. 



Differs from C. vulcanus Billings, in the pronounced char- 

 acter of the conical spur, the absence of a sigmoid flexure in the 

 posterior pair of glabellar furrows, the shortness of the two anterior 

 pairs, and the front angles of the margin. Described from a cast 

 the surface of which is smooth. 



