NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 99 



shallow furrow in front. A pair of deep pits in furrow at anterior 

 corners of glabella. Three shallow pairs of lateral furrows visible on 

 upper surface. Occipital furrow deep at the sides, shallow medially; 

 occipital ring long (sag.), bearing a node. Preglabellar field swollen 

 in posterior portion, rising above the frontal portion of the axial fur- 

 row, downsloping in anterior portion ; border furrow wide with strong 

 curvature on midline, giving it an angular aspect. Border about half 

 as long (sag.) as preglabellar field, upturned, convex, tapering at the 

 sides. Entire frontal area half as long as glabella inclusive of occipital 

 ring. Palpebral area slightly more than half as wide as glabella, slightly 

 convex and upsloping from the axial furrow. Ocular ridges distinct, 

 moderately slanted backward. Palpebral lobes defined by furrow even 

 on outer surface, fairly wide, not rising above palpebral area, 0.4 times 

 as long as glabella. Distance from palpebral lobe to posterior cranidial 

 margin considerably shorter than palpebral lobe. Anterior sections of 

 facial suture moderately divergent as in Aphelaspis, straight to border 

 furrow. Posterior area as in Aphelaspis, narrower (tr.) than occipital 

 ring. Free cheek with well-defined, convex border and border furrow ; 

 ocular platform more convex than in species of Aphelaspis ; genal 

 spine short, rapidly tapered, flat on upper side. 



Thorax preserved in complete exoskeletons in shale. One small 

 individual appears to have 12 segments; however, the larger thorax 

 illustrated herein, attached to the pygidium but lacking the cephalon, 

 shows 13 segments, and this seems to be the number in the holaspid, 

 as in the species of Aphelaspis where the thorax is known. The pleurae 

 are straight proximally, curving backward to short falcate extension 

 distally, and are furrowed through all their length, much as in Aphe- 

 laspis. 



Pygidium with considerable convexity. Axis occupying one-third 

 of the width, almost reaching margin, strongly elevated, showing 3 to 

 5 distinct rings plus terminal section, rounded posteriorly. Pleural 

 platforms steeply downsloping, with strong furrows and distinct inter- 

 pleural grooves. Border flat, wide at the sides, almost vanishing 

 medially, as the axis almost attains the margin. Anterior margin curv- 

 ing backward, almost attaining longitudinal course; angles fairly 

 sharp; posterior margin straight laterally, forming fairly sharp angle 

 medially. 



Surface of cranidium finely and densely granulate except in the 

 furrows. Border of cranidium and free cheek with terrace lines. Ocular 

 platform granulate like the cranidium. Ornamentation of pygidium 

 indistinct. Length of largest cranidium 6.5 mm. Fragments indicate 

 that the species attains a somewhat larger size. Length of largest 

 pygidium 2.4 mm., width 6 mm. 



Discussion. — This trilobite, obviously a very close relative of Aphe- 



