28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I28 



ally somewhat shallower and with a slight inbend. Palpebral area 

 slightly convex and definitely downsloping, 0.4 times as wide as the 

 glabella at its midpoint. Ocular ridges not greatly elevated ; palpebral 

 lobes slightly less than 0.3 times as long as the glabella ; distance from 

 posterior end of palpebral lobe to posterior margin twice length of 

 palpebral lobe; position of palpebral lobes somewhat in advance of 

 glabellar midpoint. Posterior limbs three-fourths as wide (tr.) as the 

 occipital ring, furrowed to the distal end. Anterior facial sutures 

 approximately parallel from eye to marginal furrow, then curving 

 inward and becoming ventral-intramarginal. Posterior branch directed 

 straight outward and backward for a considerable distance, curving 

 backward close to posterior margin. Upper surface of test faintly 

 punctate. Length of cranidium 7.5 mm. 



Remarks. — This species does not possess the characters of any 

 described Lower Cambrian genus. However, it does not seem proper 

 to erect a species, and much less a genus, on a single individual. 

 Possibly a new genus could include this form and the somewhat 

 similar associated species Antagmus? longifrons. 



Occurrence. — Boulder M-9, Metis. 



Disposition of material. — U.S.N.M. No. 123877, 



Periommellinae Rasetti, new subfamily 



The aberrant genvts Periommella seems to warrant a separate sub- 

 family. 



Ptychopariidae with very wide fixed cheeks, palpebral area folded 

 down vertically in front and at the sides, causing the eyes to be con- 

 cealed in dorsal view. Posterior limbs not extending farther laterally 

 than the palpebral area. Pygidium unknown, presumably very small. 

 Known only from the upper Lower Cambrian of the Appalachian 

 province. 



Genus PERIOMMELLA Resser, 1938 



Description. — Cranidium proportionately wide and short. Glabella 

 truncatoconical, high posteriorly, sloping down anteriorly, of low 

 longitudinal convexity ; glabellar furrows indistinct, occipital furrow 

 impressed, occipital ring long (sag.), elevated. Dorsal furrow very 

 deep at the sides, narrower and shallower in front. Frontal area con- 

 sisting of short (sag.) preglabellar field and prominent, convex border. 

 Preglabellar area with tendency to develop a median boss. The border 

 may be strongly arched transversely {P. roddyi). Palpebral area flat, 

 upsloping, twice as wide as the glabella, folded down vertically in 



