NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 72i 



Occurrence. — Uppermost Aphelaspis zone, in association with 

 Aphelaspis tarda. The type locality is cnw/14. Shields Ridge. Also in 

 collections cnw/20, Washburn, and cnu/7, Purchase Ridge, Scott 

 County, Va. 



ry/^^.y.— Holotype : U.S.N.M. 144628. Paratypes: U.S.N.M. 

 144629-31. 



DUNDERBERGIA LONGEFRONS Rasetti, new species 



Plate 15, figures 13-18 



Available material. — Several cranidia and one pygidium. 



Description. — Glabella strongly convex transversely and fairly con- 

 vex longitudinally, slightly tapered, rounded in front, with 2 pairs of 

 shallow lateral furrows. Occipital furrow deep, occipital ring lacking a 

 distinct node. Frontal area relatively short ; preglabellar field steeply 

 downsloping; border convex, elevated. Palpebral area convex trans- 

 versely, on the average horizontal ; ocular ridges low and broad ; pal- 

 pebral lobes well defined by furrow even on outer surface, slightly more 

 anterior with respect to the glabella than in the preceding species. 

 Anterior section of facial suture weakly divergent; posterior section 

 and posterior area not entirely preserved. 



Pygidial axis broad, elevated, showing two very distinct rings and 

 a terminal section with a third shallow ring furrow ; axis extended into 

 a broad postaxial ridge. Pleural regions with 3 distinct pairs of broad 

 furrows; interpleural grooves lacking. Border furrow broad, border 

 narrow, poorly defined. The posterior outline shows a faint median 

 notch in dorsal view and is elevated medially in posterior view. 



Surface of both shields covered with moderately elevated granules. 

 Length of largest (holotype) cranidium 6 mm. Length of pygidium 

 L3 mm., width 2.4 mm. 



Discussion. — The species differs from D. tennesseensis and most 

 other forms of the genus in the proportionately longer glabella relative 

 to the entire cranidium. 



Occurrence. — U.S.G.S. collection 2970, Monroe County. The asso- 

 ciation of species at that locality indicates the middle Aphelaspis zone. 



Ty/'^.y.— Holotype : U.S.N.M. 144632. Paratypes: U.S.N.M. 

 144633. 



Family PTEROCEPHALIIDAE Kobayashi, 1935 



Genus APHELASPIS Resser, 1935 



Type species. — Aphelaspis walcotti Resser. 



The study of the species of Aphelaspis, from the southern Appala- 

 chians presents such taxonomic problems as may be expected when 

 thousands of individuals from numerous localities and slightly differ- 



