NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — ^RASETTI 97 



axial furrow laterally. Occipital furrow and ring as in Aphelaspis. 

 Frontal area less than half the glabellar length, downsloping. Pregla- 

 bellar field slightly convex ; border narrow, elevated. Palpebral area 

 narrow, upsloping; palpebral lobe elevated, opposite anterior third of 

 glabella. Posterior area narrower (tr.) than occipital ring, broadly 

 triangular, rather strongly downsloping. Anterior section of facial 

 suture as in Aphelaspis. Free cheek wide, steeply downsloping ; ocular 

 platform somewhat convex ; border narrow. Facial suture cutting pos- 

 terior margin rather far from genal angle; genal spine short and 

 slender. Size small. Surface smooth except for puncta in the depres- 

 sions. 



Discussion. — The close affinity with Aphelaspis is obvious. Never- 

 theless the genus appears to deserve recognition because of the greater 

 relief of the cranidial parts, in particular the elevation of the palpebral 

 area and lobe and the downsloping attitude of the free cheek and 

 posterior area. Another distinguishing feature is the anterior position 

 of the eyes. The cranidia of Paraphelaspis resemble immature cranidia 

 of Aphelaspis rather than adult individuals of that genus. Possibly 

 we have a case of paedogenesis, Paraphelaspis representing an offshoot 

 of the Aphelaspis stock preserving immature features in sexually ma- 

 ture individuals. 



One should also mention the resemblance of the genus to Kujandas- 

 pis Ivshin (type species: Kujandaspis kujandensis Ivshin, 1956), 

 which seems also to represent another close relative of Aphelaspis. In 

 Kujandaspis the glabella is relatively smaller and the eyes do not have 

 such an anterior position as in Paraphelaspis. 



Type species. — Paraphelaspis vigilans Rasetti, n. sp. 



Occurrence. — Aphelaspis zone of the southern Appalachians. 



PARAPHELASPIS VIGILANS Rasetti, new species 



Plate 21, figures 14-28 



Available material. — Numerous cranidia and free cheeks. 



Description. — Glabella strongly tapered, truncate in front, defined 

 by a deep axial furrow at the sides, a shallower furrow in front. One 

 or two shallow pairs of lateral furrows visible even on outer surface, 

 of the same pattern as in Aphelaspis. Occipital furrow well marked ; 

 occipital ring bearing a node. Frontal area 0.4 to 0.5 times as long as 

 glabella plus occipital ring, proportionately longer in larger cranidia. 

 Preglabellar field with a more or less pronounced convexity in front 

 of the glabella; border furrow regularly curved; border length (sag.) 

 less than half the preglabellar field ; border convex, elevated. Pal- 

 pebral area very narrow, proportionately wider in larger cranidia, 

 more or less strongly upsloping; ocular ridges distinct, very short, 

 directed somewhat forward. Palpebral lobe somewhat less than 0.3 



