NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 103 



ville area. A considerable amount of variability is present in the 

 cranidia; since the various forms intergrade and occur in the same 

 bed, it would be improper to split the species, even though the ex- 

 tremes in the range of variation might suggest such action. 



The main variable features are the convexity of the glabella and 

 the entire cranidium; the depth of the axial furrow; the direction of 

 the occipital spine, varying from almost horizontal to upturned at 45 

 degrees ; the distinctness of the occipital furrow ; the relative width 

 and convexity of the anterior border. The figured cranidia show some 

 of these features. The largest cranidium has a length of 15 mm. exclu- 

 sive of the spine. 



The pygidium, although less common than the cranidium, can be 

 assigned with virtual certainty. It is about twice as wide as long, 

 regularly rounded posteriorly. Axis occupying almost entire length, 

 tapered, with 3 prominent rings and a terminal section, bearing a large 

 upright spine on the first ring. Pleural lobes convex and downsloping, 

 with 3 pairs of broad pleural furrows and 2 pairs of narrower inter- 

 pleural grooves, all reaching almost to the margin; border furrow 

 shallow, border narrow, poorly defined. Length of largest pygidium 

 9 mm,, width 18 mm. 



The pygidium closely resembles that of Shickshockia cristata (Ra- 

 setti, 1946), and the cranidium also has similar features. It is ques- 

 tionable whether Shickshockia should be maintained as a distinct 

 genus. 



Occurrence. — Uppermost beds of Maryville and basal beds of Noli- 

 chucky formation (Cedaria zone). Type locality is U.S.N.M. 123a, 

 4 miles NE. of Rogersville. Collected by the author at localities cnc/1 

 to cnc/6 in the Maryville limestone and localities cnd/1, cnd/2 in the 

 red beds of the Nolichucky. 



7^;/?^.^.— Holotype : U.S.N.M. 61719. Paratypes: U.S.N.M. 

 61721, 61722. Plesiotypes: U.S.N.M. 144703-6. 



Genus CHEILOCEPHALUS Berkey, 1898 



Type species. — Cheilocephalus stcroixensis Berkey. 



CHEILOCEPHALUS BREVILOBUS (Walcott) 



Plate 17, figures 1-5 



Lisania? hreviloba Walcott, 1916b, p. 404, pi. 66, figs. 3-3c. 



Pseudolisania breviloba (Walcott) Kobayashi, 1935, p. 162. 



Pseudolisania breviloba (Walcott) Resser, 1938a, p. 96, pi. 16, fig. 17. 



Cheilocephalus breviloba (Walcott) Palmer, 1954, p. 759, pi. 88, figs. 1-4 (in- 

 cludes complete synonymy up to 1954) . 



Cheilocephalus brevilobus (Walcott) Lochman and Hu, 1962b, p. 436, pi. 69, 

 figs. 1-24. 



