NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 69 



the cranidial surface has fewer and smaller granules than H. granu- 

 latus; these are barely apparent on the glabella and frontal area, being 

 more conspicuous on the palpebral and posterior areas. The pygidium 

 has the same structure as in H. granulatus, but here again the granules 

 are indistinct. The species attains a larger size, with cranidia 3^ mm. 

 in length. This form may be ancestral to H. granulatus. 



Occurrence. — Uppermost beds of Maryville limestone {Cedaria 

 zone) at locality cnc/1. 



Tj;/)^.?.— Holotype : U.S.N.M. 144621. Paratypes: U.S.N.M. 

 144622. 



Family CEDARIIDAE Raymond, 1937 



Genus CEDARIA Walcott, 1924 



Type species. — Cedaria prolifica Walcott. 



CEDARIA TENNESSEENSIS Walcott 



Plate 5, figures 4-8 



Cedaria tennesseensis Walcott, 1925, p. 79, pi. 17, figs. 22-25. 

 Cedaria tennesseensis Walcott, Resser, 1938a, p. 68, pi. 11, figs. 3-5. 



Available material. — The types are cranidia, free cheeks, and py- 

 gidia flattened in shale. Fragmentary material in limestone was col- 

 lected by the writer. 



Description. — Cranidium of moderate convexity. Glabella as in other 

 species of the genus. Frontal area sharply divided into preglabellar 

 field and border by a narrow border furrow ; border flat, its sagittal 

 length more than half the length of the preglabellar field. Palpebral 

 area and lobe without specific features. Posterior area broad (exsag.), 

 the posterior section of the facial suture running outward and slightly 

 forward ; border furrow on posterior area turning forward for a con- 

 siderable distance. Anterior sections of facial suture less divergent 

 than in most other species of the genus. Free cheek with ocular plat- 

 form and border of about equal widths, separated by sharp border 

 furrow, Genal spine long and strong as in other species of Cedaria. 



Pygidium 1.6 times as wide as long, almost elliptical, with anterior 

 angles widely rounded. Axis short, in larger individuals not exceeding 

 half of the pygidial length, showing about 3 rings plus a terminal sec- 

 tion. Pleural regions almost flat, wide, with 3 pairs of broad, shallow 

 furrows and a trace of a fourth, and indistinct interpleural grooves. 

 The furrows run straight through the pleural platform, change to a 

 more backward direction in passing onto the wide, slightly concave 

 border, and almost reach the pygidial margin. Pygidial doublure very 

 wide, its anterior margin well visible as an impression on the dorsal 

 side. Pygidial border with very fine, wavy lines. 



Discussion. — This species differs considerably from the type species, 



