NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 89 



of length of preglabellar field. Frontal area averaging slightly over 0.6 

 times the glabellar length. Palpebral area rising above the axial fur- 

 row, somewhat convex, on average somewhat upsloping, half as wide 

 as glabella. Ocular ridges stronger than in most species, transverse 

 to slightly slanted forward. Palpebral lobes 0.4 times the glabellar 

 length ; distance from posterior end of palpebral lobe to posterior 

 margin equal to length of palpebral lobe. Posterior area as wide (tr.) 

 as occipital ring. Free cheek with flat genal spine of average rate of 

 tapering. 



Pygidium about 3 times as wide as long. Axis with 2 rings plus a 

 terminal section. Pleural lobes showing only 1 distinct pair of pleural 

 furrows. 



Length of largest cranidium observed 7 mm. 



Discussion. — This species resembles A. lata but is clearly distin- 

 guished by the depth of the axial furrow, convexity of the palpebral 

 area, wider anterior border, and smoother pygidium. 



Occurrence. — Locality cnp/17, Hurricane Hollow, in the basal bed 

 of the Aphelaspis zone, a few feet above strata with typical Crepi- 

 cephalus fauna. 



Ty/)^.r.— Holotype : U.S.N.M. 144663. Paratypes: U.S.N.M. 

 144664. 



APHELASPIS MINOR Rasetti, new species 



Plate 19, figures 18-25 



Available material. — Large numbers of cranidia and free cheeks, 

 and a few pygidia. 



Description. — Glabella of average shape and convexity; occipital 

 furrow fairly well impressed, occipital ring bearing a low node. Pre- 

 glabellar field moderately convex longitudinally; border furrow well 

 impressed, slightly angular on midline; border convex, its midlength 

 (sag.) less than the length of preglabellar field. Length of frontal area 

 averaging 0.50 times length of glabella plus occipital ring. Palpebral 

 area upsloping ; palpebral lobes slightly elevated above palpebral area, 

 set off by shallow furrow, half the length of glabella plus occipital ring. 

 Distance from posterior end of palpebral lobe to posterior cranidial 

 margin less than length of palpebral lobe. Ocular ridges transverse. 

 Anterior sections of facial suture with average divergence. Posterior 

 area about as wide (tr.) as occipital ring. Free cheek with rather flat 

 border defined by sharp change in slope. Genal spine relatively long, 

 rather flat on dorsal side. 



Pygidium exactly 3 times as wide as long. Axis well tapered, 

 rounded posteriorly, showing 2 rings plus a terminal section, reaching 

 the border furrow. Pleural platforms rather convex, faintly furrowed. 



