358 SYSTEMATIC PALEONTOLOGY 



" Pygidium wider than long, more or less subtrigonal in outline, but 

 with the anterior margin broadly rounded. Axis well defined, convex, 

 extending nearly to the posterior margin, with five or six transverse seg- 

 ments, which grow fainter posteriorly. The pleurae convex, each with 

 about five segments, which are furrowed distally. Whole surface of the 

 test minutely granular." Weller, 1903. 



The fragments of this species noted in the basal part of the Martins- 

 burg shale agree in all characters with the New Jersey Trenton specimens 

 described in detail by Weller as above. 



Occurrence. MARTINSBURG SHALE (Sinuites bed). Chambersburg, 

 Pennsylvania, and Strasburg, Virginia. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Family CHEIRURIDAE 



Genus GERAURUS Green 



CERAURUS PLEUREXANTHEMUS Green 



Plate XLIII, Figs. 22, 23 



Ceraurus pleurexanthemus Green, 1832, Monthly Amer. Jour. Geol., vol. 1, 



p. 560, pi. iv, fig. 10. 

 Ceraurus pleurexanthemus Green, 1832, Mono. Trilobites North America, 



p. 84, text fig. 10, cast 33. 

 Ceraurus pleurexanthemus Hall, 1847, Pal. New York, vol. i, p. 242, pi. Ixv, 



figs, la-c, le-g. 

 Ceraurus pleurexanthemus Weller, 1903, Geol. Surv. New Jersey, Pal., 



vol. iii, p. 204, pi. xv, fig. 28. 

 Ceraurus pleurexanthemus Raymond and Benton, 1913, Bull. Mus. Comp. 



Zool., vol. liv, p. 528, pi. i, fig. 1; pi. ii, figs. 1, 2, 7. 



Description. " Head crescentif orm in outline, with the posterior 

 lateral angles extended into long, curved, genal spines, which are attached 

 to the fixed cheeks. Free cheeks irregularly triangular in outline, the 

 eyes small. Facial suture starting at the lateral margin, and after 

 extending inward toward the glabella, making a sharp turn forward just 

 back .of the eye, and after passing around the eye, curving gently for- 

 ward, cutting the anterior margin of the head in front of the glabella. 

 Glabella prominent, convex, broadest in front, extending nearly to the 



