NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 5 



apparently visible on most unexfoliated cranidia. Occipital ring heavy 

 and of nearly even width throughout. Brim consists of a simple bar 

 of even width throughout, and never as long as the glabella is wide. 

 It may be somewhat thickened and has various attitudes with respect 

 to the horizontal plane. Eyes always very large, strongly bowed, and 

 set off by a clearly defined palpebral furrow. Fixigenes confined to 

 the large palpebral lobes between the eyes and dorsal furrow. Because 

 the eyes usually extend far forward, they continue part way around 

 the anterior angles. At the rear they may extend behind the ends of 

 the occipital furrow, but if not, only very narrow and short postero- 

 lateral limbs are formed. 



Libragenes narrow and long. Ocular platform narrow, long, and 

 curved somewhat less than the eye. Outer rim usually clearly defined, 

 increasing in width toward the genal angle. Genal spines present. 

 They vary from short to long slender spines several times the cranidial 

 length. They are usually directed outward at a considerable angle to 

 the axis. Some Wisconsin species, however, appear to have long 

 curved genal spines which cross over the thorax to the extent that 

 their outer extremities overlap. 



Hypostoma nearly circular in outline, large, and characterized by a 

 large central lobe. The alate portions are upturned toward the edges. 



Pygidium ovate, with about half the area of the cranidium. The 

 well-segmented axis is wide and long but tapers little. From two to 

 four rings are defined and the terminal lobe may have faint impres- 

 sions of others. The pleural platforms are convex, usually less than 

 half the axial width at the same point, and drop off into a narrow 

 flattened border. 



Surface smooth. 



Genotype. — C. whitfieldi Hall. 



The fragment described by Raymond as Chariocephalus peloris 

 (Bull. Geol. Soc. Amer., vol. 48, No. 8, p. 11 19, pi. 3, fig. 12, 1937) 

 is excluded from the genus by its small eye, and the direction and 

 depth of the glabellar furrows. 



As stated above, Kobayashi's Irvingella {Irving ellina) protuherans 

 (Jap. Journ. Geol. Geogr., vol. 5, Nos. 3-4, p. 176, pi. 15, figs, la-c, 

 2, 1938) falls into CJiariocephalus. 



CHARIOCEPHALUS TENERUS, new species 

 Plate i, Figures 1-3 



This moderately small species, represented by a single almost 

 entirely exfoliated cranidium, is the only example of the genus found 

 in this collection. 



