NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 47 



CREPICEPHALUS, species undetermined No. 1 



Plate 8, figures 17, 18 



Available material. — Represented by incomplete, exfoliated pygidia 

 and one poorly preserved cranidium that may belong to the same 

 species. 



Description. — Pygidium twice as wide as long. Axis occupying 

 about five-sixths of the length, somewhat tapered, showing 3 rings and 

 a terminal section. Pleural lobes extended into a pair of broad-based, 

 strongly outward-directed, and presumably very long spines. Pleural 

 platforms relatively short, with 3 pairs of pleural furrows. Border 

 furrow indistinct. 



Discussion. — This form cannot be identified with any described 

 species on account of the character of the pleural spines. 



Occurrence. — Uppermost beds of the lower limestone member 

 (Crepicephalus zone) of the Nolichucky (loc. cnn/4). 



Disposition of material. — Figured specimens: U.S.N.M. 144570. 



CREPICEPHALUS? species undetermined No. 2 



Plate 8, figures 12, 13 



Available material. — A few cranidia and pygidia tentatively assigned 

 to one species, preserved in limestone as internal impressions. 



Description. — Glabella rather strongly convex in both directions, 

 straight-sided, tapered, rounded in front, unfurrowed. Occipital furrow 

 well impressed, straight; occipital ring lacking node or spine. Pre- 

 glabellar field very short ; border sharply elevated, convex, somewhat 

 arched transversely ; border furrow lacking depressions. Palpebral area 

 slightly upsloping, about 0.25 times glabellar width; palpebral lobes 

 small, curved, opposite glabellar midpoint; ocular ridges faintly indi- 

 cated. Anterior facial sutures slightly divergent; anterior angles of 

 cranidium narrowly rounded. Posterior area not preserved. 



Associated pygidium of the Crepicephalus type, twice as wide as the 

 midlength. Axis long, showing 3 rings and a terminal section, extended 

 into a short postaxial ridge that reaches the margin. Pleural platforms 

 convex and downsloping, with 3 pairs of deep, wide furrows, ending 

 at wide, shallow border furrow. Spines continue the straight, slightly 

 convergent outline of pygidial sides and are sharply pointed without 

 attaining great length ; margin between spines forming a broad curve. 

 Length of largest cranidium 16 mm. ; of pygidium 7 mm., width 14 mm. 



Discussion. — The pygidium seems definitely to belong in the genus ; 

 the cranidium, however, is unusual in the strongly elevated anterior 

 border and slightly upsloping palpebral area. The first of these char- 

 acters would rather suggest Meteoraspis, but in that genus the pal- 

 pebral area rises above the axial furrow and then slopes downward in 

 characteristic fashion. 



